Single-photon pulse laser radar target detection method and system

Abstract

The invention provides a single photon pulse laser radar target detection method and system. The method comprises the following steps: modulating pulse emission time delay by adopting a pseudo-random number function to obtain a pulse laser emission time sequence; a precise time-to-digital converter is adopted to collect output signals of the single-photon detector, the arrival time of photons is recorded, and an echo photon time sequence is obtained; the method comprises the following steps: intercepting echo photon time subsequences in a pulse laser emission time sequence according to a fixed length sequence, delaying the echo photon time subsequences in combination with an echo photon time sequence delay amount to obtain a delay subsequence, and carrying out matching counting on the delay subsequence and the echo photon time sequence to obtain a matching counting number; continuously adjusting delay to obtain a matching function; and performing threshold detection on the matching function, and calculating a target distance by taking an echo photon time subsequence delay amount corresponding to the threshold detection as pulse round-trip flight time. According to the invention, the problem of fixed pulse repetition frequency ranging ambiguity is solved.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a single-photon pulse laser radar target detection method and system. Background Art

[0002] Laser radar can achieve longer distance and high-precision ranging due to its small beam divergence angle, concentrated energy and strong anti-interference ability. In recent years, with the development of high-power lasers, single-photon detectors and related electronics, two new detection methods have emerged in laser radar, namely single-photon pulse laser radar. The photon detector in the single-photon pulse laser radar system can respond to photons, thereby achieving longer distance measurement. At present, the ranging technology of single-photon pulse laser radar is developing rapidly and is mainly used for ranging of cooperative targets: With the technological advancement of single-photon pulse laser radar, it also shows potential advantages in non-cooperative target detection, which can solve the problem of traditional radar in detecting drone cluster targets.

[0003] Due to the extremely high sensitivity of photon detectors, photon counting is required in a low background noise environment to achieve target detection. In recent years, research on time-correlated photon counting methods has been carried out at home and abroad, making full use of the correlation characteristics of target photons to effectively extract target echo photons mixed in the noise. The emergence of time-to-digital converters has further promoted the development of single-photon ranging, which can convert the collected time signal into a digital signal. However, the current single-photon pulse lidar signal processing mainly adopts offline processing methods, which achieves target detection, ranging and imaging by accumulating a large amount of signal data: but this signal processing method cannot meet the requirements for non-cooperative target detection. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a single-photon pulse laser radar target detection method and system, which solves the problem of non-cooperative target detection and ranging ambiguity of the existing single-photon laser radar.

[0005] The technical solution of the method of the present invention is a single-photon pulse laser radar target detection method, comprising the following steps:

[0006] Step 1: Use a pseudo-random number function to modulate the pulse emission time delay to obtain a pulse laser emission time sequence;

[0007] Step 2: Use a precision time-to-digital converter to collect the output signal of the single-photon detector, record the arrival time of the photon, and obtain the echo photon time series;

[0008] Step 3: intercept the echo photon time subsequence in a fixed length order in the pulse laser emission time sequence, delay the echo photon time subsequence in combination with the delay amount of the echo photon time sequence to obtain a delayed subsequence, match and count the delayed subsequence with the echo photon time sequence to obtain the matching count number, and continuously adjust the delay to obtain the matching function;

[0009] Step 4: Perform threshold detection on the matching function, use the delay of the echo photon time subsequence corresponding to the threshold detection as the round-trip flight time of the pulse, and calculate the target distance;

[0010] Preferably, the pulse laser emission time sequence in step 1 is defined as follows:

[0011]

[0012] Among them, i is the transmission pulse number, counting from 1, pt i is the emission time of the i-th pulse laser, f is the laser pulse repetition frequency, and α is a pseudo-random number between [0,1).

[0013] Preferably, the echo photon time series described in step 2 is defined as follows:

[0014] [t j ,t j+1 ,…,t j+m ]

[0015] Where j is the received photon number, starting from 1, t j is the arrival time of the jth photon recorded by the single-photon detector;

[0016] Preferably, the echo photon time subsequence in step 3 is:

[0017] [pt i ,pt i+1 ,…,pt i+K ]

[0018] Where K represents the length of the echo photon time subsequence, pt i+k is the emission time of the i+kth pulse laser;

[0019] Preferably, the delay subsequence described in step 3:

[0020] [pt i +τ,pt i+1 +τ,…,pt i+k +τ]

[0021] Among them, τ is the delay of the echo photon time subsequence;

[0022] Match and count the delayed subsequence and the echo photon time series to obtain the matching count number E(τ); continuously adjust τ to obtain the matching function:

[0023]

[0024] Among them, g(τ) is the matching function;

[0025] Preferably, the matching count refers to the number of time intervals between the arrival time of photons in the echo photon time sequence and the emission time of the pulsed laser after the delay in the delay subsequence that are less than a fixed value Δt;

[0026] The specific calculation method of Δt is as follows:

[0027]

[0028] Among them, Δt pulse is the pulse laser time width, Δt jitter is the single photon detector time jitter, Δt tdc Determined by TDC time accuracy;

[0029] Preferably, the target distance is calculated in step 4 as follows:

[0030] r = τ·c / 2;

[0031] Where r is the target distance and c is the speed of light in a vacuum.

[0032] The present invention also provides a single-photon pulse laser radar target detection system, which is as follows:

[0033] Pulse laser emission time sequence modulation module, used to use pseudo-random number function to modulate the pulse emission time delay to obtain the pulse laser emission time sequence

[0034] The echo photon time series building module is used to collect the output signal of the single photon detector using a precision time-to-digital converter, record the arrival time of the photon, and obtain the echo photon time series;

[0035] A matching function building module is used to intercept the echo photon time subsequence in a fixed length order in the pulse laser emission time sequence, delay the echo photon time subsequence in combination with the delay amount of the echo photon time sequence to obtain a delayed subsequence, match and count the delayed subsequence with the echo photon time sequence to obtain the matching count number, and continuously adjust the delay to obtain the matching function;

[0036] The target distance calculation module is used to perform threshold detection on the matching function, and use the echo photon time subsequence delay corresponding to the threshold detection as the pulse round-trip flight time to calculate the target distance.

[0037] Compared with the prior art, it has the following beneficial effects:

[0038] Based on the fixed pulse laser emission repetition rate, the present invention introduces a random delay in the pulse emission time, realizes target detection signal detection by matching and counting the emission pulse sequence and the echo photon sequence, solves the problem of fixed pulse repetition rate ranging ambiguity, and can be applied to a larger laser pulse repetition rate range. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 : A flow chart of a method according to an embodiment of the present invention;

[0040] Figure 2 : Schematic diagram of random modulation of pulse emission time delay of the single-photon pulse laser radar target detection method according to an embodiment of the present invention;

[0041] Figure 3 : A matching schematic diagram of the single-photon pulse laser radar target detection method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In specific implementation, the method proposed in the technical solution of the present invention can be implemented by technical personnel in this field using computer software technology to realize automatic operation process. System devices for implementing the method, such as computer-readable storage media storing the corresponding computer program of the technical solution of the present invention and computer equipment running the corresponding computer program, should also be within the scope of protection of the present invention.

[0044] Combine the following Figures 1 to 3 The specific implementation of the present invention is a single-photon pulse laser radar target detection method, which includes the following steps: (1) randomly modulating the pulse emission time delay; (2) recording the original data of the photon arrival time; (3) calculating the matching function of the pulse laser emission time series and the echo photon time series; (4) realizing target signal detection and ranging through the matching function. This method solves the problem of fixed pulse laser emission repetition rate ranging ambiguity by introducing random time delay in the pulse laser emission cycle and combining it with the echo photon matching count, and can be applied to a larger laser pulse repetition rate range.

[0045] like Figure 1The method flow chart of an embodiment of the present invention is a single-photon pulse laser radar target detection method, comprising the following steps:

[0046] Step 1: Use a pseudo-random number function to modulate the pulse emission time delay to obtain the pulse laser emission time sequence, see Appendix Figure 2 ;

[0047] The pulse laser emission time sequence described in step 1 is defined as follows:

[0048]

[0049] Among them, i is the transmission pulse number, counting from 1, pt i is the emission time of the i-th pulse laser, f=6000 is the laser pulse repetition frequency, and α is a pseudo-random number between [0,1).

[0050] Step 2: Use a precision time-to-digital converter to collect the output signal of the single-photon detector, record the arrival time of the photon, and obtain the echo photon time series;

[0051] The echo photon time series described in step 2 is defined as follows:

[0052] [t j ,t j+1 ,…,t j+m ]

[0053] Where j is the received photon number, counting from 1, t j is the arrival time of the jth photon recorded by the single-photon detector;

[0054] Step 3: intercept the echo photon time subsequence in a fixed length order in the pulse laser emission time sequence, delay the echo photon time subsequence in combination with the delay amount of the echo photon time sequence to obtain a delayed subsequence, match and count the delayed subsequence with the echo photon time sequence to obtain the matching count number, and continuously adjust the delay to obtain the matching function;

[0055] The echo photon time subsequence described in step 3 is:

[0056] [pt i ,pt i+1 ,…,pt i+K ]

[0057] Where K represents the length of the echo photon time subsequence, pt i+k is the emission time of the i+kth pulse laser;

[0058] The delay subsequence described in step 3:

[0059] [pt i+τ,pt i+1 +τ,…,pt i+k +τ]

[0060] Among them, τ is the delay of the echo photon time subsequence;

[0061] Match and count the delayed subsequence and the echo photon time series to obtain the matching count number E(τ); continuously adjust τ to obtain the matching function:

[0062]

[0063] Among them, g(τ) is the matching function;

[0064] The matching count refers to the number of time intervals between the arrival time of photons in the echo photon time sequence and the delayed pulse laser emission time in the delay subsequence that are less than a fixed value Δt, see Appendix Figure 3 ;

[0065] The specific calculation method of Δt is as follows:

[0066]

[0067] Among them, Δt pulse The pulse laser time width can be 3ns, Δt jitter The single photon detector time jitter is 300ps, Δt tdc 10ps is determined by the TDC time accuracy;

[0068] Step 4: Perform threshold detection on the matching function, use the delay of the echo photon time subsequence corresponding to the threshold detection as the round-trip flight time of the pulse, and calculate the target distance;

[0069] Step 4 calculates the target distance as follows:

[0070] r = τ·c / 2;

[0071] Where r is the target distance and c is the speed of light in a vacuum.

[0072] The system embodiment of the present invention is a single-photon pulse laser radar target detection system, which is specifically as follows:

[0073] Pulse laser emission time sequence modulation module, used to use pseudo-random number function to modulate the pulse emission time delay to obtain the pulse laser emission time sequence

[0074] The echo photon time series building module is used to collect the output signal of the single photon detector using a precision time-to-digital converter, record the arrival time of the photon, and obtain the echo photon time series;

[0075] A matching function building module is used to intercept the echo photon time subsequence in a fixed length order in the pulse laser emission time sequence, delay the echo photon time subsequence in combination with the delay amount of the echo photon time sequence to obtain a delayed subsequence, match and count the delayed subsequence with the echo photon time sequence to obtain the matching count number, and continuously adjust the delay to obtain the matching function;

[0076] The target distance calculation module is used to perform threshold detection on the matching function, and use the echo photon time subsequence delay corresponding to the threshold detection as the pulse round-trip flight time to calculate the target distance.

[0077] Table 1: Multiple measurements of target distance (example)

[0078] Number of measurements 1 2 3 4 5 RMS Flight time 220.156 220.146 220.137 220.151 220.141 0.006794 Target distance 33023.4 33021.9 33020.55 33022.65 33021.15 1.0191

[0079] The pulse laser emission time series modulation module, echo photon time series construction module, matching function construction module and target distance calculation module are all deployed on the server.

[0080] It should be understood that parts not elaborated in detail in this specification belong to the prior art.

[0081] It should be understood that the above description of the embodiments is relatively detailed and cannot be regarded as limiting the scope of patent protection of the present invention. Under the enlightenment of the present invention, ordinary technicians in this field can also make substitutions or modifications without departing from the scope of protection of the claims of the present invention, which all fall within the scope of protection of the present invention. The scope of protection requested by the present invention shall be based on the attached claims.

Claims

1. A single-photon pulse laser radar target detection method, characterized in that: The following steps are involved: Step 1: Use a pseudo-random number function to modulate the pulse emission time delay to obtain a pulse laser emission time sequence; Step 2: Use a precision time-to-digital converter to collect the output signal of the single-photon detector, record the arrival time of the photon, and obtain the echo photon time series; Step 3: intercept the echo photon time subsequence in a fixed length order in the pulse laser emission time sequence, delay the echo photon time subsequence in combination with the delay amount of the echo photon time sequence to obtain a delayed subsequence, match and count the delayed subsequence with the echo photon time sequence to obtain the matching count number, and continuously adjust the delay to obtain the matching function; Step 4: Perform threshold detection on the matching function, and use the delay of the echo photon time subsequence corresponding to the threshold detection as the round-trip flight time of the pulse to calculate the target distance.

2. The single photon pulse laser radar target detection method according to claim 1, characterized in that: The pulse laser emission time sequence described in step 1 is defined as follows: Among them, i is the transmission pulse number, counting from 1, pt i is the emission time of the i-th pulse laser, f is the laser pulse repetition frequency, and α is a pseudo-random number between [0,1).

3. The single photon pulse laser radar target detection method according to claim 2, characterized in that: The echo photon time series described in step 2 is defined as follows: [t j ,t j+1 ,…,t j+m ] Where j is the received photon number, starting from 1, t j is the arrival time of the jth photon recorded by the single-photon detector.

4. The single photon pulse laser radar target detection method according to claim 3, characterized in that: The echo photon time subsequence described in step 3 is: [pt i ,pt i+1 ,…,pt i+K ] Where K represents the length of the echo photon time subsequence, pt i+k is the emission time of the i+kth pulse laser; The delay subsequence described in step 3: [pt i +t,pt i+1 +t,…,pt i+k +t] Among them, τ is the delay of the echo photon time subsequence.

5. The single photon pulse laser radar target detection method according to claim 4, characterized in that: Match and count the delayed subsequence and the echo photon time series to obtain the matching count number E(τ); continuously adjust τ to obtain the matching function: Among them, g(τ) is the matching function.

6. The single photon pulse laser radar target detection method according to claim 5, characterized in that: The matching count refers to the number of times that the time interval between the arrival time of the photon in the echo photon time sequence and the time of the pulse laser emission after the delay in the delay subsequence is less than a fixed value Δt; The specific calculation method of Δt is as follows: Among them, Δt pulse is the pulse laser time width, Δt jitter is the single photon detector time jitter, Δt tdc Determined by the TDC time accuracy.

7. The single photon pulse laser radar target detection method according to claim 6, characterized in that: Step 4 calculates the target distance as follows: r = τ·c / 2; Where r is the target distance and c is the speed of light in a vacuum.

8. A single photon pulse laser radar target detection system, characterized in that: Pulse laser emission time sequence modulation module, used to use pseudo-random number function to modulate the pulse emission time delay to obtain the pulse laser emission time sequence The echo photon time series building module is used to collect the output signal of the single photon detector using a precision time-to-digital converter, record the arrival time of the photon, and obtain the echo photon time series; A matching function building module is used to intercept the echo photon time subsequence in a fixed length order in the pulse laser emission time sequence, delay the echo photon time subsequence in combination with the delay amount of the echo photon time sequence to obtain a delayed subsequence, match and count the delayed subsequence with the echo photon time sequence to obtain the matching count number, and continuously adjust the delay to obtain the matching function; The target distance calculation module is used to perform threshold detection on the matching function, and use the echo photon time subsequence delay corresponding to the threshold detection as the pulse round-trip flight time to calculate the target distance.

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