Ocean laser radar waveform photonizing and post-pulse removing method and system

Abstract

The invention discloses an ocean laser radar waveform photonizing and post-pulse removing method. According to the method, single photon response calibration is completed by utilizing probability histogram distribution of single photon output integral values of a photomultiplier (PMT), and photonization processing of original echo waveforms acquired by the ocean laser radar is realized; and the post-pulse probability is calibrated to realize quantitative removal of the post-pulse. The experimental device comprises a signal generator, a laser, a digital adjustable attenuator, a photomultiplier (PMT), a data acquisition card and an upper computer processing module, and the stability of system triggering and data acquisition is ensured. According to the technical scheme, through single-photon calibration based on the integral value, continuous analog sampling and uniform representation of the photon number of discrete single-photon output waveform signals are completed, interference of post-pulse on weak signals of the ocean laser radar is eliminated, the measurement precision and reliability are improved, and the device has the advantages of being simple in structure, convenient to operate and accurate in calibration and has a wide application prospect. The method is suitable for the high-precision ocean laser radar detection field.

Description

Technical Field

[0001] This invention relates to the field of marine lidar signal processing technology, and in particular to a waveform photonics and post-pulse removal method and system based on photomultiplier tube (PMT) single-photon response calibration, which is applicable to the field of high-precision marine lidar detection. Background Technology

[0002] Lidar systems, especially marine lidar, have become important tools for profiling the optical properties of water bodies, monitoring phytoplankton distribution, and mapping seabed topography. Their working principle involves emitting laser pulses and receiving their backscattered signals to retrieve the optical parameters of the water body. Due to the strong attenuation effect of seawater on light signals, lidar echo signals exhibit a wide dynamic range: the near-field region shows a strongly scattered signal, appearing as a continuous analog waveform; as depth increases, the signal rapidly attenuates to the single-photon level, appearing as a discrete pulse signal. This drastic change in signal characteristics places extremely high demands on detector performance and signal processing technology.

[0003] To achieve a high signal-to-noise ratio, photomultiplier tubes (PMTs) are typically used to receive echo signals. However, in practical detection, mechanisms such as ion feedback inherent in PMTs during operation introduce backpulse signals with significant time delays, interfering with the identification and quantitative analysis of effective signals. One type is the instantaneous backpulse with a short delay, usually appearing within tens of nanoseconds after the signal pulse, primarily caused by ion feedback between the first two electrodes in the PMT's multiplication structure. The other type is the slow backpulse with a longer delay, reaching hundreds of nanoseconds or even microseconds, mainly caused by ion drift after ionization of residual gas near the anode. The latter type significantly interferes with echo identification in deeper water areas of lidar signals, especially when analyzing weak signals in deep water regions (e.g., water depths exceeding 20 meters with delays greater than 100 ns).

[0004] Currently, several technical solutions have attempted to address the aforementioned problems. For example, patent document CN112504482B discloses a method for measuring and suppressing afterpulse probability based on a single-photon avalanche photodiode (SPAD). Based on a SPAD detector, it identifies and merges afterpulses by setting a time interval threshold, adjusts parameters using digitally controlled resistors and capacitors, and plots a histogram of afterpulse probability based on the pulse distribution, thereby achieving the identification and optimization of the system's afterpulse effect. However, its main focus is on the performance optimization testing of the SPAD device, and it does not solve the waveform processing problem of mixed-mode signals already acquired by marine lidar. Its method is based on counter statistics and cannot achieve photonization and point-by-point afterpulse removal of analog waveforms or photon-counted signals, making it unsuitable for accurate quantitative analysis of complex waveforms in marine lidar.

[0005] Therefore, there is an urgent need to develop a new technical solution that can simultaneously solve the two closely related technical challenges of high-precision photonics of full dynamic range waveforms and quantitative separation and removal of complex afterpulse noise, thereby significantly improving the accuracy and reliability of marine lidar, especially its deep-water detection capabilities. Summary of the Invention

[0006] The purpose of this invention is to provide a waveform photonics conversion and afterpulse removal method based on photomultiplier tube (PMT) single-photon response calibration. This method aims to accurately convert analog waveforms into photon counts and quantitatively remove afterpulse noise generated by the PMT, thereby improving the accuracy of lidar data processing and the system signal-to-noise ratio. Under anechoic conditions, the method calibrates the PMT's single-photon response integral value and afterpulse probability, using these as quantitative bases for subsequent waveform processing. In the post-processing of actual marine lidar echo signals, the acquired analog waveform is converted into photon counts using the single-photon calibration value. Subsequently, combining the signal pulse size with the laboratory-calibrated afterpulse probability distribution, the afterpulse interference signal is calculated and removed. This method is simple to operate, does not rely on large-scale statistical model training, significantly improves the accuracy of data inversion, and is applicable to various lidar systems and detection scenarios, especially marine lidar systems with continuous analog output characteristics.

[0007] The technical solution of the present invention is as follows:

[0008] A method for wave photonics conversion and post-pulse removal in marine lidar, characterized by the following steps:

[0009] (a) Single-photon response calibration: In a dark room environment, the light intensity incident on the photomultiplier tube is controlled to make it work in the single-photon response state. The waveform data output by the photomultiplier tube is collected. After baseline correction and noise suppression preprocessing, the effective single-photon events that meet the amplitude threshold and pulse width conditions are identified. The integral values ​​of all effective single-photon events are counted and their probability distribution histogram is plotted. The weighted average of the integral value distribution is calculated as the single-photon response calibration value.

[0010] (b) Afterpulse probability calibration: Based on the single-photon response calibration value, the waveform data containing signal pulses acquired synchronously are uniformly photonicized, the signal pulse region is identified and its total number of photons is counted, the afterpulse event at each delay time is identified, and the distribution function of the afterpulse probability as a function of the delay time is established.

[0011] (c) Unified processing of radar echo: The voltage signal of the actual collected marine lidar echo waveform is converted into a photon number waveform based on the single photon response calibration value; the number of photons generated by the signal pulse at each delay time is calculated based on the distribution function of the afterpulse probability as a function of the delay time; the number of photons of the afterpulse is quantitatively subtracted from the corresponding position in the photonized waveform to obtain the real echo signal.

[0012] The weighted average of the integral value distribution in step (a) is calculated by using a probability weighting method based on the histogram of the probability distribution of single-photon integral values.

[0013] Furthermore, the unified photonics processing in step (b) refers to: without distinguishing between analog strong signals and discrete photonic signals, using the same single-photon response calibration value to convert all voltage amplitudes into photon counts, thereby achieving a unified quantitative characterization of the mixed signal mode.

[0014] Furthermore, the post-pulse events in step (b) include direct post-pulse events and multi-stage cascaded post-pulse events.

[0015] Furthermore, the identification of the multi-level cascaded afterpulse includes: by analyzing the temporal correlation between the afterpulse event and the preceding pulse, identifying the afterpulse directly triggered by the signal pulse, as well as the secondary and higher-level afterpulse events triggered by the afterpulse itself.

[0016] The method includes the following steps:

[0017] The digital attenuator is adjusted to bring the incident light signal to a near-single-photon response level. A single-photon loss rate of approximately 50% is used as a criterion to determine that the PMT is in a single-photon response state.

[0018] Under this condition, at least 10,000 waveform data points are continuously collected;

[0019] Set a voltage threshold, filter out single-photon pulses, and extract their amplitude, pulse width, and integral value;

[0020] Calculate the integral values ​​of all valid single-photon pulses and plot a histogram;

[0021] Calculate the weighted average of the integral value histogram, which will serve as a reference value for single-photon calibration in subsequent photonics processing.

[0022] The photonics method employs a time resolution (1 ns) consistent with the original waveform sampling rate. The voltage amplitude of each sampling point is divided by the calibrated single-photon response reference value according to the following formula, and then converted into waveform data in units of "photon count", thereby realizing the unified quantization of analog signals and discrete single-photon signals.

[0023]

[0024] in, For the number of photons, The waveform voltage amplitude, This is the single-photon calibration value.

[0025] The photonic waveform after this processing can be used for subsequent steps such as afterpulse probability calibration.

[0026] Secondly, this invention proposes a device and method for calibrating the probability characteristics of afterpulses, used to achieve afterpulse removal. The device is consistent with the single-photon calibration system, including: a signal generator, a laser, a digitally adjustable attenuator, a PMT detector, a data acquisition card, and a host computer processing module. It is similar in structure to the single-photon response calibration device, but has the ability to synchronously control the laser.

[0027] in:

[0028] The signal generator outputs a pulse signal with a repetition rate of 10MHz and a pulse width of 5ns, which is used to trigger the laser to emit laser pulses and to provide a synchronous trigger signal to the data acquisition card.

[0029] The laser outputs green light with a wavelength of 532nm;

[0030] The digitally adjustable attenuator is used to adjust the laser incident intensity;

[0031] The PMT detector is a HAMAMATSU H10720P-210 model, and the gain voltage depends on the requirements.

[0032] The data acquisition card acquires echo waveforms with laser emission as the time reference;

[0033] The host computer is used for data storage and post-pulse statistical processing.

[0034] The method includes the following steps:

[0035] Under the condition of synchronous control of the laser and the data acquisition system, complete data including signal pulses and subsequent waveforms is acquired;

[0036] Identify the time position of the signal pulse, and count the delay time of the subsequent pulse relative to the signal pulse and the number of subsequent pulse events at that delay time;

[0037] The distribution function of the post-pulse probability Rate as a function of time delay is established using the following formula;

[0038]

[0039] in, The number of subsequent pulse events. The number of photons in the signal pulse (photonics according to the first invention of this invention), This represents the number of waveforms counted.

[0040] This probability model can be used in practical waveform processing: based on the number of photons in the signal pulse and the delay time, the contribution of the afterpulse at each sampling point of the signal pulse is calculated by a probability function and subtracted from the original waveform to achieve quantitative removal of the afterpulse signal.

[0041] Compared with the prior art, the advantages of the present invention are as follows:

[0042] 1. Achieving unified photonic characterization of analog detection and photon counting detection: The photonic characterization method proposed in this invention is based on PMT single-photon response calibration, which can convert continuous analog waveforms, discrete photon counting waveforms and mixed waveforms with a unified processing flow. It does not require switching or classification based on differences in system acquisition modes, ensuring the compatibility and uniformity of data acquired by different types of marine lidar systems, and is conducive to the standardization of subsequent processing flow.

[0043] 2. Supports multi-type afterpulse identification and deep-sea pseudo-signal removal: This invention accurately calibrates the afterpulse probability and removes the signal point by point on the basis of photonics. It can not only identify and quantify short-delay afterpulses caused by the multiplier tube preamp, but also effectively eliminate secondary afterpulse signals formed by the superposition of afterpulses. It is especially suitable for the removal of afterpulse pseudo-signals in deep water with a wavelength of more than 200ns, which significantly improves the accuracy and effective depth of deep-sea detection.

[0044] 3. Meets the requirements of large dynamic range and deep-water detection calibration for marine lidar: This invention obtains single-photon response values ​​and afterpulse probability curves through precise experimental calibration, avoiding reliance on empirical models or specific thresholds. It ensures stable and accurate photonics processing and afterpulse removal across the entire dynamic range from strong near-field signals to weak deep-water signals, significantly improving the system's detection capability and stability in complex environments such as long distances and high water attenuation. Attached Figure Description

[0045] Figure 1 This is a flowchart of the method for photonicization and quantitative removal of afterpulse from marine lidar echo waveforms according to the present invention;

[0046] Figure 2 This is a schematic diagram of the system for implementing the marine lidar waveform photonics conversion and post-pulse removal method of the present invention:

[0047] In the diagram: 1 – Signal generator, 2 – Laser, 3 – Digitally adjustable attenuator, 4 – PMT detector, 5 – Data acquisition card, 6 – Host computer processing module

[0048] Figure 3(a) is a preprocessed single-photon waveform diagram in this invention;

[0049] Figure 3 (b) is a histogram of the single-photon integral value of the photomultiplier tube in this invention;

[0050] Figure 4 (a) is a diagram of the preprocessed post-pulse waveform and a schematic diagram of post-pulse identification in this invention;

[0051] Figure 4 (b) is a graph showing the probability distribution of the afterpulse of the photomultiplier tube in this invention.

[0052] Figure 5 (a) is a schematic diagram of the waveform before photonicization in this invention.

[0053] Figure 5 (b) is a schematic diagram of the waveform after photonicization in this invention.

[0054] Figure 6 This is a schematic diagram comparing the waveforms before and after the removal of the post-pulse in this invention. Detailed Implementation

[0055] The present invention will be further described below with reference to embodiments and accompanying drawings, but this should not be construed as limiting the scope of protection of the present invention.

[0056] I. Overall Process Introduction

[0057] Please see Figure 1 , Figure 1 This is a flowchart of the method for photonics conversion and quantitative removal of afterpulse from marine lidar echo waveforms according to the present invention. It includes the following main steps:

[0058] 1. Single-photon response calibration: The single-photon response calibration value of the PMT is obtained by measurement under weak light excitation conditions, which is used for subsequent photonics processing;

[0059] 2. Afterpulse probability calibration: Identify afterpulse events and calculate the afterpulse probability of PMT at different delay times;

[0060] 3. Radar waveform processing in practical applications:

[0061] (1) Photonic conversion of echo signal: The measured original echo waveform signal is converted into a photon number waveform while maintaining the original time resolution of the waveform;

[0062] (2) Calculation and removal of afterpulse photon count: Based on the known afterpulse probability, the afterpulse interference is estimated and removed to achieve quantitative correction of the lidar echo waveform.

[0063] II. Experimental Setup and System Configuration

[0064] Please see Figure 2 , Figure 2 This is a schematic diagram of the experimental system for implementing the method of wave photonics conversion and post-pulse removal of marine lidar according to the present invention. As shown in the figure, the system includes:

[0065] Signal generator 1 outputs a high-repetition-rate, narrow-pulse-width pulse signal (10MHz repetition rate, 5ns pulse width), which is simultaneously connected to the external trigger input of laser 2 and data acquisition card 5 to provide a synchronous trigger signal. Upon receiving the trigger signal, laser 2 outputs a 532nm pulsed laser. The laser light is attenuated by a digitally adjustable attenuator 3 controlled by the host computer processing module 6 before illuminating the PMT detector 4. The PMT's gain voltage is set to 5V. The analog signal output from the PMT's anode is sampled and recorded by data acquisition card 5, and the host computer processing module 6 centrally controls the triggering, data acquisition, and processing flow of the entire system.

[0066] III. Implementation of Single-Photon Response Calibration

[0067] The specific steps for single-electron response calibration are as follows:

[0068] Step 1: System Initialization and Single-Photon State Adjustment

[0069] The signal generator is set with a pulse width of 5ns, a high level of 2.5V, a low level of 0V, and a repetition frequency of 10MHz.

[0070] The laser outputs 532nm pulsed light; adjust the laser beam path to accurately focus the laser onto the PMT's receiving window. Turn on the oscilloscope, set the bandwidth limit to 20MHz, and disable the persistence function; gradually adjust the digitally adjustable attenuator to reduce the laser power and observe the oscilloscope waveform; when 5 to 10 pulse signals with amplitudes significantly higher than the dark count appear in each waveform screenshot, the system is considered to have entered the single-photon response working state.

[0071] Step 2: Data Acquisition and Preprocessing

[0072] Connect the PMT output to the data acquisition card, use the host computer software to acquire tens of thousands of waveform data, and save the corresponding PMT model and experimental parameters.

[0073] Calculate the average value of the last 50 sampling points of each waveform as the baseline noise level, and subtract this baseline from the entire waveform;

[0074] To suppress the influence of electronic noise, circuit noise signals with an amplitude less than 5 are set to zero; please refer to [link / reference]. Figure 3 (a) is the preprocessed single-photon waveform.

[0075] Step 3: Single-photon event identification and integration statistics:

[0076] Signals with a peak value greater than or equal to 5 and a pulse width greater than or equal to 2 sampling points are identified as valid single-photon events. The identified single-photon events are integrated, the integral values ​​are calculated, and a histogram of the integral values ​​is constructed. (See [link to relevant documentation]). Figure 3 (b) is the single-photon histogram of the photomultiplier tube.

[0077] Step 4: Calculation of Single-Photon Response Calibration Value

[0078] according to Figure 3 (b) Integral histogram, calculate the weighted average integral value as the single-photon response calibration value of PMT.

[0079] IV. Implementation of Afterpulse Probability Calibration

[0080] After completing the single-photon calibration, post-pulse probability calibration is performed:

[0081] Step 1: Signal source setup and data acquisition

[0082] The signal generator is set with a pulse width of 5ns, a high level of 2.5V, a low level of 0V, and a repetition frequency of 10MHz.

[0083] Precisely align the optical path so that the laser beam enters the PMT receiving window completely;

[0084] By adjusting the digitally adjustable attenuator to reduce the laser power, the peak value of the PMT output signal pulse is made to be about half of the saturation level, so as to obtain a clear and stable signal pulse response.

[0085] Under stable laser parameters, connect the PMT output signal to the data acquisition card;

[0086] Tens of thousands of waveform data points were collected using host computer software, and the PMT model used was marked.

[0087] Step 2: Data Preprocessing

[0088] The average of the last 50 sampling points of each waveform is used as the baseline noise level, and this value is subtracted from the entire waveform.

[0089] Signals with an amplitude less than 5 are considered noise and set to zero to avoid electronic noise affecting subsequent peak identification. Please refer to [link to relevant documentation]. Figure 4 (a) is the waveform of the preprocessed pulse.

[0090] Step 3: Waveform photonics processing

[0091] The voltage amplitude at each sampling point of the waveform is divided by the single-photon response reference value obtained from the invention calibration using the following formula, and converted into waveform data in units of "photon count":

[0092]

[0093] in, For the number of photons, The waveform voltage amplitude, This is the single-photon calibration value.

[0094] Identify the signal pulse region, integrate its photon count, and obtain...

[0095] Step 4: Identification of Post-Pulse Events

[0096] Scanning the waveform segment 200ns and beyond from the maximum value of the signal pulse, the time delay is defined as the time between the peak value of the signal pulse and the peak value of the subsequent pulse. Figure 4 As shown in (a);

[0097] A valid pulse event is defined as a signal with a peak value greater than or equal to 5 and a pulse width greater than or equal to 2 sampling points. Figure 4 As shown in (a);

[0098] Count the number of subsequent pulse events within each delay time period of a sufficient number of waveforms.

[0099] Step 5: Construct the post-pulse probability distribution curve

[0100] The afterpulse probability is defined as the probability that a photon in a signal pulse will generate an afterpulse event at the specified delay time. It is calculated using the following formula:

[0101]

[0102] in, The number of subsequent pulse events. The number of photons in the signal pulse (photonics according to the first invention of this invention), This represents the number of waveforms counted. For example... Figure 4 (b) shows the afterpulse probability curve of the photomultiplier tube being measured.

[0103] V. Implementation of Actual Radar Echo Processing

[0104] Based on the aforementioned single-photon response calibration value and afterpulse probability, quantitative removal of afterpulses from the marine lidar echo waveform is achieved, specifically including the following steps:

[0105] Step 1: Photonicization of Echo Signal

[0106] Using the following formula, the voltage signals at each sampling point of the acquired original echo waveform signal are successively divided by the single-photon response calibration value to convert them into photon number waveform data, thereby realizing waveform photonization.

[0107]

[0108] in, For the number of photons, The waveform voltage amplitude, This is the single-photon calibration value. Please refer to [link / reference]. Figure 5 , Figure 5 (a) is the waveform before photonicization. Figure 5 (b) shows the waveform after photonics conversion. This step ensures that the resolution of the photonics waveform is consistent with that of the original waveform.

[0109] Step 2: Calculate the number of photons in the post-pulse.

[0110] The signal pulse region in the photonic waveform is identified, and the number of photons at each sampling point of the signal pulse is multiplied by the probability of the subsequent pulse at the corresponding delay time to calculate the number of subsequent pulse photons at that delay time. The total number of subsequent pulse photons at a given sampling point is then the sum of the number of subsequent pulse photons generated by the signal pulse at that sampling point.

[0111] Step 3: Remove post-pulse

[0112] The number of photons in the afterpulse calculated in step two is subtracted from the number of photons at the corresponding delay time position in the photonic waveform signal to achieve quantitative removal of the afterpulse; please refer to Figure 6 This diagram illustrates the waveform comparison before and after removing the afterpulse, as presented in this invention. By calibrating the single-photon calibration value and the afterpulse probability, the interference of the afterpulse on the waveform signal is effectively suppressed, improving the accuracy and reliability of the marine lidar detection results.

[0113] This invention addresses the issues of photonics processing and afterpulse removal in simulated waveforms from marine lidar systems, proposing a quantitative processing method based on laboratory calibration. By measuring the integral value of the single-photon response and the afterpulse probability, the afterpulse signal is quantitatively removed, significantly improving the accuracy of waveform processing and the system signal-to-noise ratio. Furthermore, relying on experimental calibration results, this method effectively simplifies the afterpulse processing workflow and is applicable to the general processing needs of various waveform types and detection tasks in marine lidar systems.

[0114] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for oceanic lidar waveform photonization and post-pulse removal, characterized in that, The method comprises the following steps: (a) Single photon response calibration: in a darkroom environment, by controlling the light intensity incident to the photomultiplier tube to work in a single photon response state, collecting the waveform data output by the photomultiplier tube, after baseline correction and noise suppression preprocessing, identifying the effective single photon events satisfying the amplitude threshold and pulse width conditions, counting the integral values of all effective single photon events and drawing a probability distribution histogram thereof, and calculating the weighted average value of the integral value distribution as a single photon response calibration value; (b) Post-pulse probability calibration: according to the single photon response calibration value, the waveform data containing signal pulses collected synchronously are subjected to unified photonization processing, the signal pulse region is identified and the total photon number thereof is counted, the post-pulse events at each delay time are identified, and a distribution function of the post-pulse probability changing with the delay time is established; (c) Radar echo unified processing: the actually collected marine laser radar echo waveform voltage signal is subjected to photonization conversion based on the single photon response calibration value to obtain a photon number waveform; based on the distribution function of the post-pulse probability changing with the delay time, the post-pulse photon number generated by the signal pulse at each delay time is calculated; The post-pulse photon number is quantitatively deducted from the corresponding position of the photonization waveform to obtain a true echo signal.

2. The ocean laser radar waveform photonization and post-pulse removal method according to claim 1, characterized by, The calculation method of the weighted average value of the integral value distribution in the step (a) is as follows: based on the single photon integral value probability distribution histogram, the average value is calculated in a probability weighted manner.

3. The ocean laser radar waveform photonization and post-pulse removal method according to claim 1, characterized by, The unified photonization processing in the step (b) refers to: without distinguishing analog strong signals and discrete photon signals, all voltage amplitudes are converted into photon numbers by using the same single photon response calibration value to realize unified quantitative characterization of mixed signal modes.

4. The ocean laser radar waveform photonization and post-pulse removal method according to claim 1, characterized by, The post-pulse events in the step (b) include direct post-pulses and multi-stage cascaded post-pulses.

5. The ocean laser radar waveform photonization and post-pulse removal method according to claim 4, characterized by, The identification of the multi-stage cascaded post-pulses comprises: by analyzing the time correlation of the post-pulse events and the pre-pulse, the post-pulses directly induced by the signal pulse and the secondary and above post-pulse events induced by the post-pulse itself are identified.

6. The ocean laser radar waveform photonization and post-pulse removal method according to claim 1, characterized by, The distribution function of the post-pulse probability changing with the delay time in the step (b) is expressed as follows: wherein is the number of post-pulse events, is the number of signal pulse photons, is the number of statistical waveforms.

7. The ocean laser radar waveform photonization and post-pulse removal method according to claim 1, characterized by, The post-pulse photon number calculation in the step (c) adopts a point-by-point accumulation method: the photon number of each time sampling point in the signal pulse region is multiplied by the post-pulse probability of the corresponding delay time to calculate the post-pulse photon number generated by the point at each delay position; the contributions of all signal points at the same delay position are accumulated to obtain the total post-pulse photon number distribution.

8. A system for implementing the method of any one of claims 1-7, wherein the system is a marine lidar waveform photonics and post-pulse removal system, characterized in that, It comprises: A signal generator (1) having output ends connected to a trigger input end of a laser (2) and an external trigger input end of a data acquisition card (5) respectively, for providing a synchronous trigger signal; The laser (2) outputs pulsed laser after being triggered by the signal generator (1), and the pulsed laser passes through a digital adjustable attenuator (3) for light intensity adjustment, and then is incident to a light-sensitive surface of a photomultiplier tube (4); The digital adjustable attenuator (3) receives a control signal sent by an upper computer processing module (6) to adjust the attenuation value; A photomultiplier tube (4) is connected to the analog signal input of a data acquisition card (5) through a coaxial cable, and converts the received optical signal into an electrical signal output; The data acquisition card (5) is triggered synchronously by the signal generator (1) to collect and digitize the analog waveform signal output by the PMT, and transmits the waveform data to the host computer processing module (6) through a data bus; The host computer processing module (6) is connected to the data acquisition card (5) and the digital adjustable attenuator (3) through the data bus and the control interface respectively; The host computer processing module (6) is configured to: Control the attenuation value of the digital adjustable attenuator (3) to adjust the light intensity of the incident pulsed laser; Control the data acquisition card (5) to collect and receive the collected waveform data; Perform single-photon response calibration and calculate the integral value weighted average; Perform post-pulse probability calibration to establish a distribution function of the post-pulse probability with respect to the delay time; Perform uniform photonization processing on the realized echo waveform; Perform calculation and quantitative removal of the post-pulse photon number.

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