High repetition rate high flux single-photon lidar system and data processing method

Abstract

The application belongs to the field of laser radar, and provides a high-repetition high-throughput single-photon laser radar system and a data processing method.The system comprises a signal light path part and a signal acquisition and processing part.The signal light path part comprises a high-repetition laser, a transmitting lens, a perforated mirror, a beam direction control unit, a receiving lens, a synchronous detector and a single-photon detector.The signal acquisition and processing part comprises a time-to-digital converter, a control and data processing unit and a digital-to-analog conversion module.The method comprises signal acquisition, signal interpolation, waveform construction, waveform correction and three-dimensional point cloud processing.The application reduces the amount of data synchronized by a galvanometer in a manner of downsampling or key point coding, reduces the storage, transmission and calculation resources consumed by the galvanometer synchronization signal, corrects the distorted waveform caused by the dead time, improves the inversion accuracy of the intensity and depth data of the single-photon detection laser radar system, and has the advantages of easy operation and wide application range.

Description

Technical Field

[0001] This invention relates to the field of lidar, and in particular to a high repetition rate, high throughput single-photon lidar system and data processing method. Background Technology

[0002] Single-photon detectors, capable of responding to a single photon, have reached the theoretical limit of photon detection. Single-photon lidar, leveraging its advantage in low-light detection, is applied in target detection, Earth resource mapping, and autonomous driving. However, because single-photon lidar transmits only a small amount of information per echo, it requires a long accumulation period. Furthermore, the dead time of the single-photon detector leads to signal waveform distortion. The degree of distortion is directly related to the signal flux; the higher the flux, the greater the distortion. Researchers have proposed the classic "5% rule," which aims to reduce the signal detection probability to an extremely low level below 5%.

[0003] Low throughput means that a longer acquisition time is required to obtain sufficient photon information, significantly limiting the real-time performance of the system. Low repetition rate (RF) lidar systems cannot fully utilize the performance of single-photon detectors; there are still some signal-free time intervals within a single pulse cycle, indicating a significant room for improvement in detection speed. Increasing the laser RF, based on high signal throughput, can further improve the photon information acquisition rate and detection speed. However, using high RF, high-throughput detection methods simultaneously introduces the problem of generating a large amount of data in a short time, as well as inaccurate signal strength and depth inversion due to the shielding effect coupling caused by the dead time between adjacent cycles. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a high repetition rate and high throughput single-photon lidar system and data processing method, which improves the photon information acquisition rate by using high repetition rate and high throughput to improve the system detection speed, and improves the data processing speed and signal inversion accuracy by proposing a data processing method suitable for high repetition rate and high throughput.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A high-repetition-rate, high-throughput single-photon lidar system includes: a signal optical path section and a signal acquisition and processing section; the signal optical path section includes: a high-repetition-rate laser, a transmitting lens, a perforated mirror, a beam direction control unit, a receiving lens, a synchronization detector, and a single-photon detector; the signal acquisition and processing section includes: a time-to-digital converter, a control and data processing unit, and a digital-to-analog converter module.

[0007] The high repetition rate laser is connected to the synchronization detector and the transmitting lens respectively; the receiving lens is connected to the single-photon detector; the single-photon detector is connected to the time-to-digital converter; the synchronization detector is connected to the time-to-digital converter; the time-to-digital converter is connected to the control and data processing unit and the digital-to-analog converter module respectively; the digital-to-analog converter module is connected to the control and data processing unit and the beam direction control unit respectively.

[0008] The high-repetition-rate laser is used to generate laser pulses and synchronously transmit the laser pulses to the synchronization detector and the transmitting lens; the transmitting lens is used to transmit the input laser pulses to the beam direction control unit through the perforated mirror; the beam direction control unit is used to scan the target object using the input laser pulses according to the direction adjustment command sent by the digital-to-analog converter module, receive the return signal from the target object, and transmit the return signal to the single-photon detector sequentially through the perforated mirror and the receiving lens; the single-photon detector is used to convert the return signal into an electrical signal and transmit the electrical signal to the time-to-digital converter; the time-to-digital converter is used to encode the electrical signal according to the input of the synchronization detector to obtain a timestamp signal; the control and data processing unit is used to pre-program the scanning trajectory to obtain pre-programming instructions and transmit the pre-programming instructions to the digital-to-analog converter module; the digital-to-analog converter module is used to convert the pre-programming instructions into direction adjustment instructions and provide a galvanometer synchronization signal to the time-to-digital converter through downsampling or key point encoding.

[0009] Preferably, the single-photon detector is any one of a superconducting nanowire single-photon detector, a photomultiplier tube, or a Geiger-mode avalanche photodiode.

[0010] Preferably, a high-repetition-rate, high-throughput single-photon lidar data processing method includes:

[0011] Acquire the galvanometer synchronization signal and the timestamp signal;

[0012] The spatial position of the timestamp signal is interpolated according to the photon recording time order using the nearest neighbor method to obtain the interpolated signal;

[0013] The original photon waveform signal is obtained by constructing waveforms from the galvanometer synchronization signal and the interpolation signal using a statistical accumulation method.

[0014] The original photon waveform signal is corrected using a pre-designed high-repetition-rate single-photon detection waveform correction model to obtain the corrected waveform;

[0015] The three-dimensional point cloud signal of the correction waveform is obtained by centroid method and pulse region integration, and the three-dimensional point cloud signal is processed by three-dimensional point cloud processing algorithm to obtain lidar detection image; the three-dimensional point cloud signal includes: signal depth information and signal strength information.

[0016] Preferably, the expression for the high-repetition-rate single-photon detection waveform correction model includes:

[0017] and

[0018]

[0019] Among them, P M (t i ) represents the detection probability of the i-th bin; m represents the number of integer cycles spanned by the dead time; d represents the number of bins occupied by the dead time; r represents the number of bins occupied by the pulse period time; P N (t j ) represents the probability of suppressing the detection of the j-th bin; Λ j Let be the intensity of the j-th distortion-free signal.

[0020] The present invention discloses the following technical effects:

[0021] This invention provides a high-repetition-rate, high-throughput single-photon lidar system and data processing method. By reducing the amount of data synchronized with the galvanometer through downsampling or keypoint encoding, it solves the problem of excessive storage, transmission, and computing resources consumed by conventional single-photon lidar systems, achieving more efficient acquisition of photon information. By correcting the waveform distortion caused by dead time, it solves the problem of no-signal time intervals in some non-dead-zone states still existing within a single pulse cycle, thereby improving the measurement accuracy of depth and intensity data in the single-photon detection lidar system. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A structural diagram of a high-speed, high-precision single-photon lidar detection and imaging system provided in an embodiment of the present invention;

[0024] Figure 2 A flowchart of high-speed, high-precision single-photon lidar detection and imaging process provided for embodiments of the present invention;

[0025] Figure 3 This is a system data transmission structure diagram provided in an embodiment of the present invention;

[0026] Figure 4 This diagram illustrates the principle of the high-repetition-rate single-photon detection waveform correction model provided in this embodiment of the invention.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1-High repetition rate laser, 2-Emitting lens, 3-Synchronization detector, 4-Punched mirror, 5-Beam direction control unit, 6-Receiving lens, 7-Single photon detector, 8-Time-to-digital converter, 9-Control and data processing unit, 10-Digital-to-analog converter module. Detailed Implementation

[0029] 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 only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The purpose of this invention is to provide a high repetition rate and high throughput single-photon lidar system and data processing method, which improves the photon information acquisition rate by using high repetition rate and high throughput to improve the system detection speed, and improves the data processing speed and signal inversion accuracy by proposing a data processing method suitable for high repetition rate and high throughput.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Figure 1 A structural diagram of the high-speed, high-precision single-photon lidar detection and imaging system provided in the embodiments of the present invention is shown below. Figure 1 As shown, the present invention provides a high repetition rate, high throughput single-photon lidar system, comprising: a signal optical path section and a signal acquisition and processing section; the signal optical path section includes: a high repetition rate laser 1, a transmitting lens 2, a perforated reflector 4, a beam direction control unit 5, a receiving lens 6, a synchronization detector 3, and a single-photon detector 7; the signal acquisition and processing section includes: a time-to-digital converter 8, a control and data processing unit 9, and a digital-to-analog converter module 10;

[0033] The high repetition rate laser 1 is connected to the synchronous detector 3 and the transmitting lens 2 respectively; the receiving lens 6 is connected to the single-photon detector 7; the single-photon detector 7 is connected to the time-to-digital converter 8; the synchronous detector 3 is connected to the time-to-digital converter 8; the time-to-digital converter 8 is connected to the control and data processing unit 9 and the digital-to-analog converter module 10 respectively; the digital-to-analog converter module 10 is connected to the control and data processing unit 9 and the beam direction control unit 5 respectively.

[0034] A high-repetition-rate laser 1 generates laser pulses and synchronously transmits them to a synchronization detector 3 and a transmitting lens 2. The transmitting lens 2 transmits the input laser pulses to a beam direction control unit 5 via a perforated mirror 4. The beam direction control unit 5 scans the target object using the input laser pulses according to the direction adjustment command sent by the digital-to-analog converter 10, receives the return signal from the target object, and transmits the return signal to a single-photon detector 7 via the perforated mirror 4 and a receiving lens 6. The single-photon detector 7 converts the return signal into an electrical signal and transmits the electrical signal to a time-to-digital converter 8. The time-to-digital converter 8 encodes the electrical signal according to the input from the synchronization detector 3 to obtain a timestamp signal. A control and data processing unit 9 pre-programs the scanning trajectory to obtain pre-programming instructions and transmits the pre-programming instructions to the digital-to-analog converter 10. The digital-to-analog converter 10 converts the pre-programming instructions into direction adjustment instructions and provides a galvanometer synchronization signal to the time-to-digital converter 8 through downsampling or keypoint encoding.

[0035] Optionally, the single-photon detector 7 is any one of a superconducting nanowire single-photon detector 7, a photomultiplier tube, or a Geiger-mode avalanche photodiode.

[0036] refer to Figure 2 A method for processing high-repetition-rate, high-throughput single-photon lidar data, comprising:

[0037] Acquire galvanometer synchronization signal and timestamp signal;

[0038] The spatial location of the timestamp signal is interpolated according to the photon recording time order using the nearest neighbor method to obtain the interpolated signal;

[0039] The original photon waveform signal is obtained by constructing waveforms from the galvanometer synchronization signal and the interpolation signal using a statistical accumulation method.

[0040] The original photon waveform signal was corrected using a pre-designed high-repetition-rate single-photon detection waveform correction model to obtain the corrected waveform;

[0041] The three-dimensional point cloud signal of the correction waveform is obtained by using the centroid method and pulse region integration, and the three-dimensional point cloud signal is processed by the three-dimensional point cloud processing algorithm to obtain the lidar detection image; the three-dimensional point cloud signal includes: signal depth information and signal strength information.

[0042] Specifically, the expression for the high-repetition-rate single-photon detection waveform correction model includes:

[0043] and

[0044]

[0045] Among them, P M (t i ) represents the detection probability of the i-th bin; m represents the number of integer cycles spanned by the dead time; d represents the number of bins occupied by the dead time; r represents the number of bins occupied by the pulse period time; P N (t j ) represents the probability of suppressing the detection of the j-th bin; Λ j Let be the intensity of the j-th distortion-free signal.

[0046] Specifically, the high-repetition-rate laser 1 emits laser pulses that are divided into two optical signals. One signal is received by the synchronization detector 3 and serves as the signal synchronization path. The other signal is emitted through the transmitting lens 2 and serves as the signal detection path. The laser from the signal detection path passes through the perforated reflector 4 and reaches the beam direction control unit 5. The beam direction control unit 5 can control the laser's emission direction to scan the target object. The returned signal light passes through the beam direction control unit 5 and reaches the perforated reflector 4. The perforated reflector 4 reflects the echo signal to the receiving lens 6 and then couples it into the receiving multimode fiber. The single-photon detector 7 converts the reflected photon signal into an electrical signal. The arrival time of the electrical signal is encoded into a timestamp signal by the time-to-digital converter 8. The control and data processing unit 9 uses a digital-to-analog converter to pre-program the scanning trajectory of the galvanometer. Another channel of the digital-to-analog converter serves as the galvanometer synchronization channel and is connected to the time-to-digital converter 8 for synchronization with the measured photon signal.

[0047] refer to Figure 3In this embodiment, the system uses the control and data processing unit 9 as the signal processing and control center. On one hand, it interacts with the time-to-digital converter 8, controlling its start / stop and parameter configuration. On the other hand, the control and data processing unit 9 encodes the galvanometer scanning signal and outputs it to the beam direction control unit 5 via the digital-to-analog converter module 10, thereby controlling the scanning mode of the beam direction control unit 5. The single-photon detection signal is input to the time-to-digital converter 8, and simultaneously, the digital-to-analog converter module 10 inputs the galvanometer synchronization signal to the time-to-digital converter 8. The digital-to-analog converter ensures signal synchronization between the beam direction control unit 5 and the measured photon signal.

[0048] refer to Figure 2 The photon timestamp signal and the galvanometer synchronization timestamp signal are received by a time-to-digital converter 8, and the timestamp data is transmitted to the control and data processing unit 9. The galvanometer synchronization timestamp signal corresponds one-to-one with the galvanometer voltage. Then, the spatial position is interpolated according to the photon recording time sequence using the nearest neighbor method. The interpolated photon signal is statistically accumulated to obtain the photon waveform signal, and the proposed high-repetition-rate single-photon detection waveform correction model corrects the accumulated waveform. The corrected waveform is then used to obtain signal depth and signal intensity information through the centroid method and integration over the pulse region. Finally, the three-dimensional point cloud signal is processed using a three-dimensional point cloud processing algorithm, combined with the spatial position information corresponding to each photon.

[0049] refer to Figure 4 The proposed high-repetition-rate single-photon detection waveform correction method is as follows: The dead time of a typical near-infrared single-photon detector (7) is on the order of microseconds. To increase the amount of echo photon information, a high repetition rate (PRF) can effectively improve the echo information. However, a long single-photon dead time will affect the detection probability of subsequent cycles, thus causing multi-cycle photon signal coupling problems. From the forward steady-state model of single-photon detection, it can be seen that the signal flux of the j-th bin of the echo... The distortion-free signal strength Λ in the j-th bin j It can be obtained using the following formula:

[0050]

[0051] Among them, P N (t j P represents the probability that no signal was detected during the previous dead time. M (t j The probability of detecting the j-th bin can be obtained by the following formula:

[0052]

[0053] Where, N jf is the cumulative number of signal photons. r Laser pulse repetition frequency, T a The accumulated time for each pixel can be obtained from the synchronization time difference between adjacent galvanometers. The probability P of detecting a signal in the d bins before the j-th bin is... N (t j )

[0054]

[0055] Where d represents the number of bins occupied by the dead time.

[0056] Since the single-photon detection process can reach stability in a short time, when the detection finally reaches stability, the high-repetition-rate detection waveform is equivalent to a multi-pulse laser, and the pulse period is extended to the original m = ceil(t). d / t r The number of pulses is m, which is a multiple of 1.5. Therefore, it is believed that signal inversion can be directly performed using a steady-state model during high-repetition-rate detection. The following formula can be derived from the above formula:

[0057]

[0058]

[0059] The above formula yields the cumulative number of photons in the j-th bin after correction. By cyclically correcting each bin within the cycle using the above formula, a distortion-free waveform can be obtained.

[0060] The beneficial effects of this invention are as follows:

[0061] This invention reduces the amount of data for galvanometer synchronization by downsampling or key point encoding, thereby reducing the storage, transmission, and computing resources consumed by the galvanometer synchronization signal. By correcting the waveform distortion caused by dead time, it improves the inversion accuracy of intensity and depth data in single-photon detection lidar systems. It has the advantages of being easy to operate and having a wide range of applications.

[0062] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0063] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for processing high-repetition-rate, high-throughput single-photon lidar data, characterized in that, include: Acquire galvanometer synchronization signal and timestamp signal; The spatial position of the timestamp signal is interpolated according to the photon recording time order using the nearest neighbor method to obtain the interpolated signal; The original photon waveform signal is obtained by constructing waveforms from the galvanometer synchronization signal and the interpolation signal using a statistical accumulation method. The original photon waveform signal is corrected using a pre-designed high-repetition-rate single-photon detection waveform correction model to obtain the corrected waveform; The three-dimensional point cloud signal of the correction waveform is obtained by using the centroid method and pulse region integration, and the three-dimensional point cloud signal is processed by the three-dimensional point cloud processing algorithm to obtain the lidar detection image. The three-dimensional point cloud signal includes: signal depth information and signal strength information; The expression for the high-repetition-rate single-photon detection waveform correction model includes: and ； in, Let be the detection probability of the i-th bin; The number of integer cycles that the dead time spans; The number of bins occupied by dead time; The number of bins occupied by the pulse period time; This represents the probability of suppressing the detection of the j-th bin. Let be the intensity of the j-th distortion-free signal.

2. A high repetition rate, high throughput single-photon lidar system, characterized in that, To implement the method as described in claim 1, the system comprises: a signal optical path section and a signal acquisition and processing section; the signal optical path section comprises: a high repetition rate laser, a transmitting lens, a perforated mirror, a beam direction control unit, a receiving lens, a synchronization detector, and a single-photon detector; the signal acquisition and processing section comprises: a time-to-digital converter, a control and data processing unit, and a digital-to-analog converter module; The high repetition rate laser is connected to the synchronization detector and the transmitting lens respectively; the receiving lens is connected to the single-photon detector; the single-photon detector is connected to the time-to-digital converter; the synchronization detector is connected to the time-to-digital converter; the time-to-digital converter is connected to the control and data processing unit and the digital-to-analog converter module respectively; the digital-to-analog converter module is connected to the control and data processing unit and the beam direction control unit respectively. The high-repetition-rate laser is used to generate laser pulses and synchronously transmit the laser pulses to the synchronization detector and the transmitting lens; the transmitting lens is used to transmit the input laser pulses to the beam direction control unit through the perforated mirror; the beam direction control unit is used to scan the target object using the input laser pulses according to the direction adjustment command sent by the digital-to-analog converter module, receive the return signal from the target object, and transmit the return signal to the single-photon detector sequentially through the perforated mirror and the receiving lens; the single-photon detector is used to convert the return signal into an electrical signal and transmit the electrical signal to the time-to-digital converter; the time-to-digital converter is used to encode the electrical signal according to the input of the synchronization detector to obtain a timestamp signal; the control and data processing unit is used to pre-program the scanning trajectory to obtain pre-programming instructions and transmit the pre-programming instructions to the digital-to-analog converter module; the digital-to-analog converter module is used to convert the pre-programming instructions into direction adjustment instructions and provide a galvanometer synchronization signal to the time-to-digital converter through downsampling or key point encoding.

3. A high repetition rate, high throughput single-photon lidar system according to claim 2, characterized in that, The single-photon detector is any one of a superconducting nanowire single-photon detector, a photomultiplier tube, or a Geiger-mode avalanche photodiode.

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