Single-photon ranging method and system for long-range high-speed targets

Abstract

This invention relates to a single-photon ranging method and system for long-range, high-speed targets. The ranging method includes: merging raw measurement information in units of data time precision to obtain a basic histogram set; obtaining a forward displacement histogram set and a reverse displacement histogram set through displacement; accumulating each histogram set to form a corresponding accumulated histogram; comparing the peak values ​​of each accumulated histogram; calculating the current accumulated displacement based on the comparison results, data time precision, and the previous accumulated displacement; and repeatedly changing the data time precision to approximate the actual time drift of the measured target. In this invention, by performing forward and reverse displacement compensation on the basic histogram set to compensate for the time drift caused by the high-speed movement of the target; and by repeatedly changing the data time precision, after a finite number of iterations, it is possible to approximate the actual time drift of the target's high-speed movement, ultimately obtaining the accurate distance to the target.

Description

Technical Field

[0001] This invention belongs to the field of single-photon ranging technology, and relates to a single-photon ranging method and system for long-distance high-speed targets. Background Technology

[0002] Single-photon ranging is a laser ranging technique that uses a single-photon detector. After the laser emits a pulse, the single-photon detector receives the photons reflected from the target. The distance to the target is obtained by measuring the time of flight of the photons. Due to the high sensitivity of single-photon detectors, the maximum range of single-photon ranging can reach tens or even hundreds of kilometers.

[0003] Because single-photon detectors have a dead time and output discrete pulse signals, and the output amplitude remains constant regardless of the number of photons received at any given moment, multiple superpositions are required to reconstruct the original signal during ranging. A block diagram of a current single-photon ranging system is shown below. Figure 1 As shown in the diagram, the raw signal generated by the single-photon detector and the laser synchronization signal are respectively distinguished and shaped by the first and second discriminators before being input into the time measurement module. The time measurement module writes the time information of the input signals into the memory. The time information of multiple input signals is superimposed by an adder to obtain a statistical histogram, which is then stored in the memory. The principle of the single-photon ranging system is as follows. Figure 2 As shown, noise such as detector dark counts and ambient light is randomly distributed in the time domain, while the target reflection signal, due to the fixed target distance, will repeatedly appear at a fixed position on the time axis. Therefore, after superimposing the results of multiple measurements, the height of the target signal will far exceed the noise, thus enabling the identification of the target signal. The time point corresponding to the maximum count in the histogram is the photon flight time of the measured target. Multiplying the time information of the target signal by the speed of light yields the target's distance.

[0004] When measuring long-range, high-speed targets, the energy of a single laser pulse needs to be increased to ensure photons return after long-distance attenuation due to the target's distance. With a fixed average laser power, increasing the energy of a single pulse leads to a decrease in the laser's repetition frequency, which in turn reduces the measurement frequency of the ranging system. At lower frequencies, the distance to the moving target can no longer be considered approximately constant; for example... Figure 3 As shown, the high-speed movement of the target causes the distance measured to change with each measurement, resulting in a continuous drift of the target signal's position on the time axis. Therefore, after superimposing multiple measurement results, the target signal's height cannot be superimposed because they are not at the same time point, leading to the target signal's height being comparable to noise, making it impossible to distinguish the signal. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a single-photon ranging method and system for long-distance high-speed targets.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A single-photon ranging method for long-range, high-speed targets includes the following steps:

[0008] S1. The laser sends a laser pulse signal to the target being measured;

[0009] S2. Extract time information from the output signal of the single-photon detector and the laser synchronization signal to obtain the raw measurement information;

[0010] S3. Determine the data time precision for this iteration calculation, and merge the original measurement information in units of data time precision to obtain the basic histogram group;

[0011] S4. Perform forward and reverse displacement on the basic histogram group to obtain the forward displacement histogram group and the reverse displacement histogram group.

[0012] S5. Accumulate the basic histogram group, the forward displacement histogram group, and the reverse displacement histogram group respectively to form the basic accumulated histogram, the forward accumulated histogram, and the reverse accumulated histogram.

[0013] S6. Compare the peak values ​​of the basic cumulative histogram, the forward cumulative histogram, and the reverse cumulative histogram. Based on the comparison results, the data time precision of this iteration, and the cumulative displacement calculated in the previous iteration, calculate the cumulative displacement of this iteration.

[0014] S7. Change the data time precision multiple times and repeat steps S3 to S6 to make the final cumulative displacement close to the actual time drift of the target moving at high speed, and calculate the distance of the target.

[0015] Furthermore, the smallest unit of time information in the original measurement information is denoted as 1 LSB, and 1 LSB is used as the data time precision for the last iteration calculation.

[0016] Furthermore, determine the total number of iterations n, such that (2 n-1 The values ​​of LSB·C and (N·v / f) match; where C represents the speed of light; N represents the number of measurements taken by the laser; v represents the estimated velocity of the target; and f represents the laser repetition frequency.

[0017] In each iteration of the calculation, with 2 n-i LSB represents the data time precision for this iteration; where i represents the number of iterations, 1≤i≤n.

[0018] Furthermore, in step S4, the basic histograms in the basic histogram group are sorted according to time sequence, and each basic histogram is shifted along the time axis by (j-1)·(S). i-1 +T i After obtaining the positive displacement histogram group, or the displacement (mj)·(S) of each foundation histogram along the time axis is calculated. i-1 -T i After that, a set of positive displacement histograms was obtained;

[0019] The basic histograms in the basic histogram group are shifted along the time axis by (j-1)·(S) respectively. i-1 -T i The reverse displacement histogram group is obtained, or the displacement (mj)·(S) of each basic histogram along the time axis is calculated. i-1 +T i The reverse displacement histogram group was then obtained.

[0020] Where j represents the index of each basic histogram in the basic histogram group after sorting them in chronological order; i represents the number of the current iteration calculation; S i-1 S represents the cumulative displacement calculated in the (i-1)th iteration. In the first iteration, S... i-1 =0;T i The time precision of the data calculated in the i-th iteration is indicated; m represents the number of basic histograms.

[0021] Furthermore, in step S6, the peak values ​​of the base accumulated histogram, the forward accumulated histogram, and the reverse accumulated histogram are compared, and the displacement coefficient 'a' is calculated for this iteration based on the comparison results. i Value; when the peak value of the basic cumulative histogram is the largest, a i =0; when the peak value of the forward cumulative histogram is the largest, a i =1; when the peak value of the reverse cumulative histogram is the largest, a i =-1; with (S i-1 +a i ·T i The cumulative displacement S calculated in the i-th iteration. i Among them, S i This represents the cumulative displacement calculated in the i-th iteration.

[0022] Furthermore, in step S7, the time point corresponding to the highest peak value during the last iteration is taken as the photon flight time of the target; the distance of the target is calculated based on the photon flight time and the speed of light.

[0023] Furthermore, based on the cumulative displacement S calculated in the last iteration... n Determine the photon flight distance of the target; calculate the average velocity of the target in the ranging direction based on the photon flight time and photon flight distance.

[0024] A single-photon ranging system for long-range, high-speed targets, including

[0025] A single-photon detector is used to detect a single photon and output a signal pulse;

[0026] The first discriminator is used to discriminate and shape the raw signal output by the single-photon detector after receiving photons;

[0027] A laser is used to send laser pulse signals to the target being measured and to generate synchronization signals.

[0028] The second discriminator is used to discriminate and shape the laser synchronization signal separately;

[0029] The time measurement module is used to acquire the time information of the output signals of the first discriminator and the second discriminator to form the original measurement information;

[0030] The clock unit is used to provide the operating clock for the time measurement module.

[0031] The first memory is used to store the original measurement information;

[0032] The first adder is used to merge the original measurement information in units of data time precision;

[0033] The second memory is used to store the basic histogram set, and to perform forward and reverse displacement on the basic histogram set to obtain and store the forward displacement histogram set and the reverse displacement histogram set.

[0034] The second adder is used to accumulate the basic histogram group, the forward displacement histogram group, and the reverse displacement histogram group respectively to obtain the basic accumulated histogram, the forward accumulated histogram, and the reverse accumulated histogram.

[0035] The third memory is used to store the basic accumulated histogram, the forward accumulated histogram, and the backward accumulated histogram;

[0036] The comparator is used to compare the magnitudes of the peak values ​​of the base accumulated histogram, the peak value of the forward accumulated histogram, and the peak value of the reverse accumulated histogram, and sends the comparison result to the logic unit;

[0037] The logic unit is used to ensure the data time precision of each iteration calculation, the displacement of the positive displacement of the basic histogram group, and the displacement of the negative displacement; based on the comparison result sent by the comparator, the data time precision of the current iteration calculation, and the cumulative displacement of the previous iteration calculation, the cumulative displacement of the current iteration calculation is calculated.

[0038] Furthermore, the method by which the logic unit determines the data timing precision for iterative calculations is as follows:

[0039] The smallest unit of time information in the original measurement information is denoted as 1 LSB. In each iteration of the calculation, 2... n-i LSB represents the data time precision for this iteration; where n represents the total number of iterations; i represents the number of the current iteration, 1≤i≤n;

[0040] The method by which the logic unit determines the amount of positive displacement of the basic histogram group is as follows:

[0041] The basic histograms in the basic histogram group are sorted in chronological order, and the displacement of each basic histogram along the time axis is (j-1)·(S). i-1 +T i ), or the displacement of each basic histogram along the time axis is (mj)·(S) i-1 -T i );

[0042] Where j represents the sequence number of each basic histogram in the basic histogram group after sorting them in chronological order; S i-1 S represents the cumulative displacement calculated in the (i-1)th iteration. In the first iteration, S... i-1 =0;T i The time precision of the data calculated in the i-th iteration is indicated; m represents the number of basic histograms.

[0043] The method by which the logic unit determines the displacement amount of the reverse displacement of the basic histogram group is as follows:

[0044] The basic histograms in the basic histogram group are sorted in chronological order, and the displacement of each basic histogram along the time axis is (j-1)·(S). i-1 -T i ); or the displacement of each basic histogram along the time axis is (mj)·(S) respectively. i-1 +T i ).

[0045] Furthermore, the method for the logic unit to calculate the cumulative displacement in this iteration is as follows:

[0046] The logic unit calculates the shift coefficient 'a' for this iteration based on the comparison result from the comparator.i Value; when the peak value of the basic cumulative histogram is the largest, a i =0; when the peak value of the forward cumulative histogram is the largest, a i =1; when the peak value of the reverse cumulative histogram is the largest, a i =-1; with (S i-1 +a i ·T i The cumulative displacement S calculated in the i-th iteration. i Among them, S i Let S0 represent the cumulative displacement calculated in the i-th iteration, and S0 = 0.

[0047] In this invention, the original measurement information is merged using data time precision as the unit to obtain a basic histogram set. This basic histogram set is then subjected to forward and reverse displacement to compensate for signal time drift caused by the high-speed movement of the target. By repeatedly changing the data time precision of the original data, after a finite number of iterations, the actual time drift of the target's high-speed movement can be approximated, ultimately obtaining the accurate distance to the target. Attached Figure Description

[0048] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0049] Figure 1 This is a block diagram of a single-photon ranging system in the prior art.

[0050] Figure 2 This is a schematic diagram of a single-photon ranging system in the prior art.

[0051] Figure 3 This is a schematic diagram illustrating the principle that existing single-photon ranging systems cannot distinguish target signals.

[0052] Figure 4 This is a flowchart of a preferred embodiment of the single-photon ranging method for long-distance, high-speed targets according to the present invention.

[0053] Figure 5 This is a schematic diagram of a single iteration calculation.

[0054] Figure 6 This is a structural block diagram of a preferred embodiment of the single-photon ranging system for long-distance, high-speed targets according to the present invention. Detailed Implementation

[0055] The following specific examples illustrate the implementation of the present invention. The illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0056] like Figure 4 As shown, a preferred embodiment of the single-photon ranging method for long-distance, high-speed targets of the present invention includes the following steps:

[0057] S1. The laser sends a laser pulse signal to the target. The laser pulse signal is reflected by the target and received by a single-photon detector.

[0058] S2. After identifying and shaping the raw signal output by the single-photon detector after receiving photons and the laser synchronization signal, the time information is extracted by the time measurement module to obtain the raw measurement information. The smallest unit of time information in the raw measurement information (i.e., the measurement accuracy of the time measurement module) is denoted as 1 LSB. The raw measurement information can be stored in the first memory for later retrieval.

[0059] S3, such as Figure 5 As shown, the data time precision for this iteration is determined. The original measurement information is merged using the data time precision as the unit to obtain multiple basic histograms. All basic histograms form a basic histogram group. Before performing this step, the total number of iterations, n, needs to be determined; the value of n is related to the estimated velocity of the measured target and needs to be such that (2 n-1 The values ​​of LSB·C and (N·v / f) are matched. Where C represents the speed of light; N represents the number of laser measurements; v represents the estimated velocity of the target; and f represents the laser repetition frequency. By selecting an appropriate value for n, (2... n-1 Matching the values ​​of LSB·C and (N·v / f) (e.g., both values ​​need to be on the same order of magnitude) ensures that most of the data obtained from multiple measurements fall within 2. n-1 Within the LSB interval, to ensure measurement accuracy. In this embodiment, it is preferable to make (2 n-1 The value of LSB·C) is approximately half the value of (N·v / f); of course, (2 n-1 The value of LSB·C can also be greater than half the value of (N·v / f).

[0060] In each iteration of the calculation, with 2 n-i LSB represents the time precision of the data in this iteration; where i represents the number of iterations, 1 ≤ i ≤ n. For example, in the first iteration, i = 1, and the time precision T1 = 2. n-1 LSB; In the second iteration, i=2, and the time precision of the data in this iteration is T2=2.n-2 LSB; In the last iteration, i = n, the time precision T of the data in this iteration is... n = 1 LSB.

[0061] S4. Please continue to refer to Figure 5 The basic histogram set is subjected to both forward and reverse displacement to obtain a forward displacement histogram set and a reverse displacement histogram set. The specific method for obtaining the forward displacement histogram set is as follows:

[0062] The basic histograms in the basic histogram group are sorted according to their chronological order, and each basic histogram is shifted along the time axis by (j-1)·(S). i-1 +T i After obtaining the positive displacement histogram, all the positive displacement histograms form a positive displacement histogram group. That is, the first basic histogram remains fixed, and each subsequent basic histogram moves (S) more than the previous basic histogram. i-1 +T i The displacement of ) . Of course, it is also possible to displace each basic histogram in the basic histogram group along the time axis by (mj)·(S) respectively. i-1 -T i This yields a group of positive displacement histograms; that is, the last basic histogram remains fixed, and each preceding basic histogram moves more (S) than the following basic histogram. i-1 -T i The displacement of ).

[0063] Where j represents the index of each histogram in the basic histogram group after sorting them in chronological order; i represents the number of the current iteration; S i-1 S represents the cumulative displacement calculated in the (i-1)th iteration. In the first iteration, S... i-1 =0;T i The time precision of the data calculated in the i-th iteration is indicated; m represents the number of basic histograms.

[0064] The specific method for obtaining the reverse displacement histogram group is as follows:

[0065] The basic histograms in the basic histogram group are shifted along the time axis by (j-1)·(S) respectively. i-1 -T i This yields a reverse displacement histogram, and all the reverse displacement histograms form a reverse displacement histogram group. That is, the first base histogram remains fixed, and each subsequent base histogram moves (S) more than the previous base histogram. i-1 -T i The displacement of ) . Of course, it is also possible to displace (mj)·(S) of each base histogram along the time axis separately. i-1 +T iThis yields a set of reverse displacement histograms; that is, the last basic histogram remains fixed, and each preceding basic histogram moves more (S) than the following basic histogram. i-1 +T i The displacement of ).

[0066] S5, please continue to refer to Figure 5 The basic histogram group, the forward displacement histogram group, and the reverse displacement histogram group are summed separately to form a basic summed histogram, a forward summed histogram, and a reverse summed histogram. Specifically, all basic histograms in the basic histogram group are summed to form a basic summed histogram; all forward displacement histograms in the forward displacement histogram group are summed to form a forward summed histogram; and all reverse displacement histograms in the reverse displacement histogram group are summed to form a reverse summed histogram.

[0067] S6. Please continue to refer to Figure 5 The peak values ​​of the basic cumulative histogram, the forward cumulative histogram, and the reverse cumulative histogram are compared. Based on the comparison results, the data time precision of this iteration, and the cumulative displacement calculated in the previous iteration, the cumulative displacement is calculated. Specifically:

[0068] The peak values ​​of the base cumulative histogram, the forward cumulative histogram, and the reverse cumulative histogram are compared, and the displacement coefficient 'a' is calculated for this iteration based on the comparison results. i Value; when the peak value of the basic cumulative histogram is the largest, a i =0; when the peak value of the forward cumulative histogram is the largest, a i =1; when the peak value of the reverse cumulative histogram is the largest, a i =-1; with (S i-1 +a i ·T i The cumulative displacement S calculated in the i-th iteration. i Among them, S i This represents the cumulative displacement calculated in the i-th iteration. That is, S1 = (a1·2) n-1 )LSB;S2=(a1·2 n-1 +a22 n-2 LSB; ...; S i =(a1·2) n-1 +a22 n-2 +……+a i 2 n -i LSB; ...; S n =(a1·2) n-1 +a22 n-2 +……+a n )LSB.

[0069] S7. Change the data time precision multiple times, i.e., with 2 n-i LSB is used as the data time precision for the i-th iteration calculation, and steps S3 to S6 are repeated. After the n-th iteration calculation, the final cumulative displacement can be made close to the actual time drift of the target moving at high speed, thereby calculating the accurate distance of the target.

[0070] The specific method for calculating the accurate distance to the target being measured is as follows:

[0071] The time point corresponding to the highest peak value (i.e., the maximum count value) after the last iteration is taken as the photon flight time of the target. The distance to the target is calculated based on the photon flight time and the speed of light. The highest peak value refers to the largest peak among the peak values ​​of the base cumulative histogram, the forward cumulative histogram, and the backward cumulative histogram formed after the last iteration. Specifically, when the peak value of the base cumulative histogram is the largest, the time point corresponding to that peak value is taken as the photon flight time of the target. When the peak value of the forward cumulative histogram is the largest, the time point corresponding to that peak value is taken as the photon flight time of the target. When the peak value of the backward cumulative histogram is the largest, the time point corresponding to that peak value is taken as the photon flight time of the target.

[0072] After calculating the photon's time of flight, the target's average velocity in the ranging direction can be further calculated, as follows:

[0073] The cumulative displacement S calculated based on the last iteration n Determine the photon flight distance of the target; calculate the average velocity of the target in the ranging direction based on the photon flight time and photon flight distance.

[0074] In this embodiment, the original measurement information is merged using data time precision as the unit to obtain a basic histogram set. This basic histogram set is then subjected to forward and reverse displacement to compensate for the signal time drift caused by the high-speed motion of the target. By repeatedly changing the data time precision of the original data, after a finite number of iterations, the actual time drift of the target's high-speed motion can be approximated, ultimately obtaining the accurate distance to the target. Furthermore, the measured time drift can also be used to calculate the target's average velocity in the ranging direction.

[0075] like Figure 6As shown, a preferred embodiment of the single-photon ranging system for long-range, high-speed targets of the present invention includes a single-photon detector, a first discriminator, a laser, a second discriminator, a time measurement module, a first memory, a first adder, a second memory, a second adder, a third memory, a comparator, and a logic unit. The single-photon detector detects a single photon and outputs a signal pulse to the first discriminator; the first discriminator discriminates and shapes the raw signal output by the single-photon detector after receiving the photon; the laser sends a laser pulse signal to the target and generates a synchronization signal to the second discriminator; the second discriminator discriminates and shapes the laser synchronization signal; and the time measurement module acquires the time information of the output signals from the first and second discriminators to form raw measurement information.

[0076] The first memory stores the original measurement information. The first adder merges the original measurement information in units of data time precision. The second memory stores a basic histogram set, and performs forward and reverse displacement on the basic histogram set to obtain and store a forward displacement histogram set and a reverse displacement histogram set. The second adder accumulates the basic histogram set, the forward displacement histogram set, and the reverse displacement histogram set to obtain a basic accumulated histogram, a forward accumulated histogram, and a reverse accumulated histogram. The third memory stores the basic accumulated histogram, the forward accumulated histogram, and the reverse accumulated histogram. The first, second, and third memories can be separate physical memories or different storage areas of the same memory. The first adder and the second adder can be separate adders or the same adder used in a time-division multiplexing manner.

[0077] The comparator compares the peak values ​​of the base accumulated histogram, the forward accumulated histogram, and the reverse accumulated histogram, and sends the comparison result to the logic unit. The logic unit determines the data time precision for each iteration, the forward displacement of the base histogram group, and the reverse displacement; based on the comparison result from the comparator, the data time precision for this iteration, and the cumulative displacement from the previous iteration, it calculates the cumulative displacement for the current iteration.

[0078] Specifically, the method by which the logic unit determines the data time precision for iterative calculations is as follows:

[0079] The smallest unit of time information in the original measurement information is denoted as 1 LSB. In each iteration of the calculation, 2... n-i LSB represents the data time precision for this iteration; where n represents the total number of iterations; i represents the number of the current iteration, 1≤i≤n.

[0080] The method by which the logic unit determines the amount of positive displacement of the basic histogram group is as follows:

[0081] The basic histograms in the basic histogram group are sorted in chronological order, and the displacement of each basic histogram along the time axis is (j-1)·(S). i-1 +T i ), or the displacement of each basic histogram along the time axis is (mj)·(S) i-1 -T i ).

[0082] Where j represents the sequence number of each basic histogram in the basic histogram group after sorting them in chronological order; S i-1 S represents the cumulative displacement calculated in the (i-1)th iteration. In the first iteration, S... i-1 =0;T i The time precision of the data calculated in the i-th iteration is indicated; m represents the number of basic histograms.

[0083] The method by which the logic unit determines the displacement amount of the reverse displacement of the basic histogram group is as follows:

[0084] The basic histograms in the basic histogram group are sorted in chronological order, and the displacement of each basic histogram along the time axis is (j-1)·(S). i-1 -T i ); or the displacement of each basic histogram along the time axis is (mj)·(S) respectively. i-1 +T i ).

[0085] The method by which the logic unit calculates the cumulative displacement in this iteration is as follows:

[0086] The logic unit calculates the shift coefficient 'a' for this iteration based on the comparison result from the comparator. i Value; when the peak value of the basic cumulative histogram is the largest, a i =0; when the peak value of the forward cumulative histogram is the largest, a i =1; when the peak value of the reverse cumulative histogram is the largest, a i =-1; with (S i-1 +a i ·T i The cumulative displacement S calculated in the i-th iteration. i Among them, S i Let S0 represent the cumulative displacement calculated in the i-th iteration, and S0 = 0.

[0087] like Figure 4 , Figure 5 and Figure 6As shown, the working principle of this embodiment will be explained below by taking the example of performing 200 ranging operations on a target with a distance of 20 kilometers and an estimated speed of about 500 m / s when the laser repetition frequency is 10 kHz and the time measurement module accuracy is 2 ns (i.e., 1 LSB = 2 ns).

[0088] First, determine the number of iterations, n.

[0089] Since N·v / f=200×500÷(10×10 3 ) = 10 (m);

[0090] When n=4, 2 4-1 ×(2×10 -9 )×3×10 8 Since m / s = 4.8 (m), the two values ​​match, so we can choose n = 4; of course, we can also choose n = 5 and perform one more iteration calculation.

[0091] During ranging, the laser sends 200 laser pulse signals to the target at a repetition frequency of 10kHz. After reflection from the target, the signals are received by a single-photon detector. The raw pulse signal generated by the single-photon detector after receiving the photons and the laser synchronization signal are respectively distinguished and shaped by the first and second discriminators before being input into the time measurement module. The time measurement module writes the time information of the photons to be measured into the first memory.

[0092] Then, the first iteration calculation is performed. A control signal is issued by the logic unit to control the first adder to perform an operation at 16ns (i.e., 2... 4-1 The measurement information in the first memory is merged in units of ×LSB to obtain a base histogram group containing multiple base histograms with a time accuracy of 16ns, and the base histogram group is stored in the second memory. The number of the base histogram group is set to "0", and the base histogram group (0) represents the base histogram group.

[0093] The histograms in histogram group (0) (i.e., the basic histogram group) are sorted according to time sequence. Each basic histogram in the basic histogram group is then shifted along the time axis by (j-1)·16ns to obtain a forward displacement histogram group, which is then stored in the second memory. Here, j represents the sequence number of each basic histogram after sorting according to time sequence. Specifically, the first basic histogram remains fixed and is directly used as the first forward displacement histogram; the second basic histogram is shifted by 16ns to become the second forward displacement histogram; the third histogram is shifted by 32ns to become the third forward displacement histogram; the fourth histogram is shifted by 48ns to become the fourth forward displacement histogram; and so on, until the final forward displacement histogram group is obtained. Of course, the positive displacement histogram group can also be obtained by shifting each basic histogram in the basic histogram group along the time axis by (mj)·(-16ns). The number of the positive displacement histogram group is set to "1", and the positive displacement histogram group is represented by histogram group (1).

[0094] The reverse displacement histograms are obtained by shifting each basic histogram in the basic histogram group along the time axis by (j-1)·(-16ns). All the reverse displacement histograms form a reverse displacement histogram group, which is then stored in a second memory. Specifically, the first basic histogram remains fixed and is directly used as the first reverse displacement histogram; the second basic histogram is shifted by (-16ns) (i.e., shifted 16ns in the reverse direction) and used as the second reverse displacement histogram; the third basic histogram is shifted by (-32ns) and used as the third reverse displacement histogram; the fourth basic histogram is shifted by (-48ns) and used as the fourth reverse displacement histogram; and so on, until the final reverse displacement histogram group is obtained. Alternatively, the reverse displacement histogram group can also be obtained by shifting each histogram in the basic histogram group along the time axis by (mj)·(16ns). Set the number of the reverse displacement histogram group to "-1", and use histogram group (-1) to represent the reverse displacement histogram group.

[0095] The basic histograms in histogram group (0) are accumulated using the second adder in chronological order (i.e., all basic histograms are accumulated) to form a basic accumulated histogram, and the result is stored in the third memory. The number of the basic histogram is set to "0", and the accumulated histogram (0) represents the basic accumulated histogram. The positive displacement histograms in histogram group (1) are accumulated using the second adder (i.e., all positive displacement histograms are accumulated) to form a positive accumulated histogram, and the result is stored in the third memory. The number of the positive accumulated histogram is set to "1", and the accumulated histogram (1) represents the positive accumulated histogram. The negative displacement histograms in histogram group (-1) are accumulated using the second adder (i.e., all negative displacement histograms are accumulated) to form a negative accumulated histogram, and the result is stored in the third memory. The number of the reverse cumulative histogram is set to "-1", and the cumulative histogram (-1) represents the reverse cumulative histogram. A comparator compares the peak values ​​of the cumulative histogram (0), the cumulative histogram (1), and the cumulative histogram (-1), and the number of the histogram with the largest peak (i.e., 1, 0, -1) is used as the value of the displacement coefficient a1 calculated in this iteration and fed back to the logic unit. That is: when the peak value of the cumulative histogram (0) is the largest, a1 = 0; when the peak value of the cumulative histogram (1) is the largest, a1 = 1; when the peak value of the cumulative histogram (-1) is the largest, a1 = -1. The cumulative displacement S1 calculated in the first iteration is 16·a1 (ns).

[0096] Then, the second iteration calculation is performed. The logic unit issues a control signal to control the first adder to merge the measurement information in the first memory in 8ns increments to form a new histogram group (0) containing multiple basic histograms with a time precision of 8ns, and stores it in the second memory. The logic unit controls the second memory to shift each basic histogram in the new histogram group (0) along the time axis by (j-1)·(16·a1+8)ns to obtain a new histogram group (1), and stores it in the second memory; shift each basic histogram in the new histogram group (0) along the time axis by (j-1)·(16·a1-8)ns to obtain a new histogram group (-1), and stores it in the second memory.

[0097] The basic histograms in the new histogram group (0), the forward displacement histograms in the new histogram group (1), and the reverse displacement histograms in the new histogram group (-1) are accumulated by the second adder in chronological order to form new accumulated histograms (0), (1), and (-1), and stored in the third memory. The peak values ​​of the new accumulated histogram (0), (1), and (-1) are compared by a comparator, and the histogram number with the largest peak value (i.e., 1, 0, -1) is fed back to the logic unit as the displacement coefficient a2 calculated in this iteration. The cumulative displacement S2 calculated in the second iteration is 16·a1 + 8·a2 (ns).

[0098] Then, the third iteration calculation is performed. The logic unit issues a control signal to control the first adder to merge the measurement information in the first memory in 4ns increments to form a new histogram group (0) containing multiple basic histograms with a time precision of 4ns, and stores it in the second memory. The logic unit controls the second memory to shift each basic histogram in the new histogram group (0) along the time axis by (j-1)·(16·a1+8·a2+4)ns to obtain a new histogram group (1), and stores it in the second memory; shift each basic histogram in the new histogram group (0) along the time axis by (j-1)·(16·a1+8·a2-4)ns to obtain a new histogram group (-1), and stores it in the second memory.

[0099] The basic histograms in the new histogram group (0), the forward displacement histograms in the new histogram group (1), and the reverse displacement histograms in the new histogram group (-1) are accumulated by the second adder in chronological order to form new accumulated histograms (0), (1), and (-1), and stored in the third memory. The peak values ​​of the new accumulated histogram (0), (1), and (-1) are compared by a comparator, and the histogram number with the largest peak value (i.e., 1, 0, -1) is fed back to the logic unit as the displacement coefficient a3 calculated in this iteration. The cumulative displacement S3 calculated in the third iteration is 16·a1 + 8·a2 + 4·a3 (ns).

[0100] Then, the fourth iteration calculation is performed. The logic unit issues a control signal to control the first adder to merge the measurement information in the first memory in units of 2ns (i.e., 1 LSB) to form a new histogram group (0) including multiple basic histograms with a time precision of 2ns, and store it in the second memory. The logic unit controls the second memory to shift each basic histogram in the new histogram group (0) along the time axis by (j-1)·(16·a1+8·a2+4·a3+2)ns to obtain a new histogram group (1), and store it in the second memory; shift each basic histogram in the new histogram group (0) along the time axis by (j-1)·(16·a1+8·a2+4·a3-2)ns to obtain a new histogram group (-1), and store it in the second memory.

[0101] The basic histograms in the new histogram group (0), the positive displacement histograms in the new histogram group (1), and the negative displacement histograms in the new histogram group (-1) are accumulated by the second adder in chronological order to form new accumulated histograms (0), (1), and (-1), and stored in the third memory. The peak values ​​of the new accumulated histogram (0), (1), and (-1) are compared by a comparator, and the histogram number with the largest peak value (i.e., 1, 0, -1) is fed back to the logic unit as the displacement coefficient a4 value for this iteration. The cumulative displacement S4 calculated in the 4th iteration is 16·a1 + 8·a2 + 4·a3 + 2·a4 (ns).

[0102] The third memory outputs the accumulated histogram (a4) (i.e., the accumulated histogram corresponding to the maximum peak value after the 4th iteration) as the optimal histogram. The time point corresponding to the maximum peak value (i.e., the maximum photon count) in the accumulated histogram (a4) is the photon flight time of the target. Multiplying the photon flight time of the target by the speed of light yields the distance of the target. Additionally, the third memory can also output the cumulative displacement S4 calculated in the 4th iteration as the cumulative displacement of the target. Multiplying the cumulative displacement S4 by the speed of light yields the distance the target has moved in the measurement direction, and thus the average velocity of the target in the measurement direction can be calculated.

[0103] In this embodiment, the original measurement information is merged using data time precision as the unit to obtain a basic histogram set. This basic histogram set is then subjected to forward and reverse displacement to compensate for the signal time drift caused by the high-speed motion of the target. By repeatedly changing the data time precision of the original data, after a finite number of iterations, the actual time drift of the target's high-speed motion can be approximated, ultimately obtaining the accurate distance to the target. Furthermore, the measured time drift can also be used to calculate the target's average velocity in the ranging direction.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A single-photon ranging method for long-range, high-speed targets, characterized in that, Includes the following steps: S1. The laser sends a laser pulse signal to the target being measured; S2. Extract time information from the output signal of the single-photon detector and the laser synchronization signal to obtain the raw measurement information; S3. Determine the data time precision for this iteration calculation, and merge the original measurement information in units of data time precision to obtain the basic histogram group; S4. Perform forward and reverse displacement on the basic histogram group to obtain the forward displacement histogram group and the reverse displacement histogram group. S5. Accumulate the basic histogram group, the forward displacement histogram group, and the reverse displacement histogram group respectively to form the basic accumulated histogram, the forward accumulated histogram, and the reverse accumulated histogram. S6. Compare the peak values ​​of the basic cumulative histogram, the forward cumulative histogram, and the reverse cumulative histogram. Based on the comparison results, the data time precision of this iteration, and the cumulative displacement calculated in the previous iteration, calculate the cumulative displacement of this iteration. S7. Change the data time precision multiple times and repeat steps S3 to S6 to make the final cumulative displacement close to the actual time drift of the target moving at high speed, and calculate the distance of the target. In step S4, the basic histograms in the basic histogram group are sorted according to time sequence, and each basic histogram is shifted along the time axis by (j-1)·(S). i-1 +T i After obtaining the positive displacement histogram group, or the displacement (mj)·(S) of each foundation histogram along the time axis, respectively. i-1 -T i After that, a set of positive displacement histograms was obtained; Displace each basic histogram in the basic histogram group along the time axis by (j-1)·(S) i-1 -T i The reverse displacement histogram group is obtained, or the displacement (mj)·(S) of each basic histogram along the time axis is calculated. i-1 +T i After that, the reverse displacement histogram group is obtained; Where j represents the index of each basic histogram in the basic histogram group after sorting them in chronological order; i represents the number of the current iteration calculation; S i-1 S represents the cumulative displacement calculated in the (i-1)th iteration. In the first iteration, S... i-1 =0; T i This indicates the time precision of the data calculated in the i-th iteration; m represents the number of basic histograms.

2. The single-photon ranging method for long-distance, high-speed targets according to claim 1, characterized in that: The smallest unit of time information in the original measurement information is denoted as 1 LSB, and 1 LSB is used as the data time precision for the last iteration calculation.

3. The single-photon ranging method for long-distance, high-speed targets according to claim 2, characterized in that: Determine the total number of iterations n such that (2 n-1 The values ​​of LSB·C) and (N· v / f The values ​​of ) match; where C represents the speed of light; and N represents the number of measurements taken by the laser. v This represents the estimated velocity of the moving target. f Indicates the repetition frequency of the laser; In each iteration of the calculation, with 2 n-i LSB represents the data time precision for this iteration; where i represents the number of iterations, 1≤i≤n.

4. The single-photon ranging method for long-distance, high-speed targets according to claim 1, characterized in that: In step S6, the peak values ​​of the base accumulated histogram, the forward accumulated histogram, and the reverse accumulated histogram are compared, and the displacement coefficient 'a' is calculated for this iteration based on the comparison results. i Value; when the peak value of the basic cumulative histogram is the largest, a i =0; when the peak value of the forward cumulative histogram is at its maximum, a i =1; when the peak value of the reverse cumulative histogram is at its maximum, a i =-1; with (S i-1 + a i ·T i The cumulative displacement S calculated in the i-th iteration. i Among them, S i This represents the cumulative displacement calculated in the i-th iteration.

5. The single-photon ranging method for long-distance, high-speed targets according to claim 4, characterized in that, In step S7, the time point corresponding to the highest peak value during the last iteration is taken as the photon flight time of the target; the distance of the target is calculated based on the photon flight time and the speed of light.

6. The single-photon ranging method for long-distance, high-speed targets according to claim 5, characterized in that, The cumulative displacement S calculated based on the last iteration n Determine the photon flight distance of the target; calculate the average velocity of the target in the ranging direction based on the photon flight time and photon flight distance.

7. A single-photon ranging system for long-range, high-speed targets, characterized in that: include A single-photon detector is used to detect a single photon and output a signal pulse; The first discriminator is used to discriminate and shape the raw signal output by the single-photon detector after receiving photons; A laser is used to send laser pulse signals to the target being measured and to generate synchronization signals. The second discriminator is used to discriminate and shape the laser synchronization signal separately; The time measurement module is used to acquire the time information of the output signals of the first discriminator and the second discriminator to form the original measurement information; The first memory is used to store the original measurement information; The first adder is used to merge the original measurement information in units of data time precision; The second memory is used to store the basic histogram set, and to perform forward and reverse displacement on the basic histogram set to obtain and store the forward displacement histogram set and the reverse displacement histogram set. The second adder is used to accumulate the basic histogram group, the forward displacement histogram group, and the reverse displacement histogram group respectively to obtain the basic accumulated histogram, the forward accumulated histogram, and the reverse accumulated histogram. The third memory is used to store the basic accumulated histogram, the forward accumulated histogram, and the backward accumulated histogram; The comparator is used to compare the magnitudes of the peak values ​​of the base accumulated histogram, the peak value of the forward accumulated histogram, and the peak value of the reverse accumulated histogram, and sends the comparison result to the logic unit; The logic unit is used to ensure the data time precision of each iteration calculation, the displacement of the positive displacement of the basic histogram group, and the displacement of the negative displacement; based on the comparison result sent by the comparator, the data time precision of the current iteration calculation, and the cumulative displacement of the previous iteration calculation, the cumulative displacement of the current iteration calculation is calculated. The smallest unit of time information in the original measurement information is denoted as 1 LSB. In each iteration of the calculation, 2... n-i LSB represents the data time precision for this iteration; where n represents the total number of iterations; i represents the number of the current iteration, 1≤i≤n; The method by which the logic unit determines the amount of positive displacement of the basic histogram group is as follows: The basic histograms in the basic histogram group are sorted in chronological order, and the displacement of each basic histogram along the time axis is (j-1)·(S). i-1 +T i ), or the displacement of each basic histogram along the time axis is (mj)·(S) respectively. i-1 -T i ); Where j represents the sequence number of each basic histogram in the basic histogram group after sorting them in chronological order; S i-1 S represents the cumulative displacement calculated in the (i-1)th iteration. In the first iteration, S... i-1 =0; T i The time precision of the data calculated in the i-th iteration is indicated; m represents the number of basic histograms. The method by which the logic unit determines the displacement amount of the reverse displacement of the basic histogram group is as follows: The basic histograms in the basic histogram group are sorted in chronological order, and the displacement of each basic histogram along the time axis is (j-1)·(S). i-1 -T i ); or the displacements of each basic histogram along the time axis are (mj)·(S) i-1 +T i ).

8. The single-photon ranging system for long-range, high-speed targets according to claim 7, characterized in that: The method by which the logic unit calculates the cumulative displacement in this iteration is as follows: The logic unit calculates the shift coefficient 'a' for this iteration based on the comparison result from the comparator. i Value; when the peak value of the basic cumulative histogram is the largest, a i =0; when the peak value of the forward cumulative histogram is at its maximum, a i =1; when the peak value of the reverse cumulative histogram is at its maximum, a i =-1; with (S i-1 + a i ·T i The cumulative displacement S calculated in the i-th iteration. i ; Among them, S i Let S0 represent the cumulative displacement calculated in the i-th iteration, and S0 = 0.

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