CN-122016679-A - Calibration and inversion method for single-photon laser radar gas detection

CN122016679ACN 122016679 ACN122016679 ACN 122016679ACN-122016679-A

Abstract

The invention provides a calibration and inversion method for single-photon laser radar gas detection, which comprises the steps of carrying out dead time correction processing on time photon counting data to obtain a time domain instrument response function, carrying out time-frequency mapping processing on the basis of the time domain instrument response function and a scanning time-frequency characteristic curve to obtain a frequency domain instrument response function, establishing a corresponding mapping relation of target gas column concentration with respect to ambient temperature and relative absorption area according to the frequency domain instrument response function, taking the mapping relation as a concentration domain instrument response function, carrying out absorbance analysis and integration on photon counting data actually measured by the single-photon laser radar on a target gas region to obtain the current relative absorption area of the target gas, inverting the column concentration of the target gas according to the ambient temperature and the current relative absorption area of the target gas region by adopting the concentration domain instrument response function, improving calibration efficiency and application range, and realizing high-precision inversion on the gas column concentration.

Inventors

LI DUAN
XU LIJUN
LV LINJIE
SUN CHONG
YAN JINYUAN
WU TIANQI
LIU QI

Assignees

北京航空航天大学

Dates

Publication Date: 20260512
Application Date: 20260128

Claims (9)

1. The calibration and inversion method for single-photon laser radar gas detection is characterized by comprising the following steps: acquiring time domain photon counting data of the single-photon laser radar under the condition of no target gas absorption and a scanning time-frequency characteristic curve of a laser light source in the single-photon laser radar; Performing dead time correction processing on the time domain photon counting data to obtain a time domain instrument response function; Based on the time domain instrument response function and the scanning time-frequency characteristic curve, time-frequency mapping processing is adopted to obtain a frequency domain instrument response function; according to the response function of the frequency domain instrument, establishing a corresponding mapping relation of the concentration of the target gas column relative to the ambient temperature and the relative absorption area as the response function of the concentration domain instrument; according to photon counting data actually measured by a single-photon laser radar on a target gas area, obtaining the current relative absorption area of the target gas through absorbance analysis and integration; And inverting the column concentration of the target gas by adopting the response function of the concentration domain instrument according to the ambient temperature of the target gas region and the current relative absorption area.
2. The calibration and inversion method for single photon lidar gas detection according to claim 1, wherein the performing dead time correction processing on the time domain photon count data to obtain a time domain instrument response function comprises: Performing dead time correction processing on the time domain photon counting data to obtain corrected photon counting waveforms; normalizing the photon counting waveform to obtain a undistorted photon counting waveform; performing noise baseline removal processing on the undistorted photon counting waveform to obtain an undistorted photon counting waveform; And carrying out pulse segmentation on the noiseless photon counting waveform to obtain the response function of the time domain instrument.
3. The method for calibrating and inverting gas detection of single-photon lidar according to claim 1, wherein the obtaining the frequency domain instrument response function based on the time domain instrument response function and the scanning time-frequency characteristic curve by using time-frequency mapping processing comprises: Acquiring a time domain interference waveform of a laser light source by using an optical dynamic frequency calibration device; Converting the time domain interference waveform into a time-frequency domain waveform through time-frequency transformation; Performing translation and scaling on the time-frequency domain waveform to obtain a scanning time-frequency characteristic curve; And mapping the scanning time-frequency characteristic curve and the time domain instrument response function according to a time axis mapping relation to obtain the frequency domain instrument response function.
4. The method for calibrating and inverting gas detection of single-photon lidar according to claim 1, wherein the establishing a corresponding mapping relation of the target gas column concentration with respect to the ambient temperature and the relative absorption area as the concentration domain instrument response function includes: Acquiring an absorption spectrum data set of target gas, wherein the absorption spectrum data set contains spectrum information under the conditions of different temperatures and different column concentrations; Performing weighted integration on the absorption spectrum data set and the response function of the frequency domain instrument to obtain pulse equivalent transmittance under different conditions; converting the pulse equivalent transmittance into pulse equivalent absorbance, and calculating a corresponding relative absorption area; Establishing a corresponding relation among temperature, column concentration and relative absorption area; fitting the corresponding relation to obtain a continuous mapping function serving as a concentration domain instrument response function.
5. The method for calibrating and inverting gas detection by single-photon lidar according to claim 4, wherein the obtaining the current relative absorption area of the target gas by absorbance analysis and integration according to photon count data actually measured by the single-photon lidar on the target gas region comprises: Performing waveform preprocessing on the actually measured photon counting data to obtain a pulse sequence; converting the pulse sequence into pulse equivalent transmittance; converting the pulse equivalent transmittance into pulse equivalent absorbance; scaling and translational matching are carried out on the pulse equivalent absorbance by least square based on a preset standard absorbance template, so as to obtain an absorbance curve; And integrating the absorbance curve to obtain the current relative absorption area.
6. The method for calibrating and inverting gas detection for single-photon lidar of claim 3, wherein mapping the scanning time-frequency characteristic curve with the time-domain instrument response function according to a time-axis mapping relationship to obtain the frequency-domain instrument response function comprises: ; Wherein, the For the frequency of the laser light, As a response function of the frequency domain instrument, As a response function of the time domain instrument, The inverse frequency-to-time mapping determined for the sweep time-frequency characteristic.
7. The method for calibrating and inverting gas detection by single photon lidar of claim 5, wherein weighting and integrating the absorption spectrum dataset and the frequency domain instrument response function to obtain pulse equivalent transmittance under different conditions comprises: ; Wherein, the The pulse equivalent transmittance for the jth pulse, As a response function of the frequency domain instrument, Is a theoretical gas transmittance spectrum curve, Is the starting frequency point of the jth pulse after being divided by the pulse in the frequency domain, Is the cut-off frequency point of the j-th pulse after being divided by the pulse; Converting the pulse equivalent transmittance to pulse equivalent absorbance, comprising: ; Wherein, the The pulse equivalent absorbance of the j-th pulse.
8. The method for calibrating and inverting gas detection by single photon lidar of claim 7, wherein integrating the absorbance curve yields a current relative absorption area comprises: ; Wherein, the Is the relative absorption area; representing the number of laser modulation pulses; equivalent absorbance for the first pulse; Represent the first Equivalent absorbance of each pulse.
9. The calibration and inversion method for single-photon lidar gas detection according to claim 8, wherein the preset standard absorbance template is selected from pulse equivalent absorbance calibration processes, the pulse equivalent absorbance is scaled and translationally matched by least square based on the preset standard absorbance template, and an absorbance curve is obtained, and the method comprises the following steps: ; ; Wherein, the S represents the amplitude scaling factor of the standard absorbance template, b represents the baseline translation factor of the standard absorbance template; is the absorbance value of the j-th pulse after scaling and translation.

Description

Calibration and inversion method for single-photon laser radar gas detection Technical Field The invention relates to the technical field of laser radar gas detection, in particular to a calibration and inversion method for single-photon laser radar gas detection. Background The single photon detector has ultrahigh sensitivity to single photon events, the detection probability of the single photon detector approaches to the quantum limit, and the single photon detector provides unprecedented capability for weak signal measurement. The single-photon laser radar based on multi-pulse code modulation further converts the limit advantage into 'hundred-meter-level' remote sensing capability, namely high signal-to-noise ratio ranging and quantitative gas leakage monitoring of hundred-meter-level non-cooperative targets can be realized under milliwatt-level average power, and an engineering 'non-contact-quantitative' means is provided for monitoring gas leakage in large industrial facilities, long-distance pipelines and complex terrains. The system acquires high-resolution 'absorption spectrum-path length' data by densely scanning the whole line type of a gas absorption line in millisecond time through a rapid wavelength tuning technology, so that the column concentration and the absorption path length of a leakage source are simultaneously given by one measurement. However, multi-pulse modulated lidar faces two major bottlenecks in field applications. Firstly, the wavelength-time response of the laser under the combined action of high-speed current modulation and temperature control is obviously nonlinear, and the transient thermal effect of a drive circuit is overlapped, so that the scanning waveform is distorted in a stretching-compressing way, the absorption peak position drifts and the line shape stretches, and the theoretical model cannot be directly matched. Secondly, in a gas strong absorption section or a short-distance high-contrast target scene, the instantaneous count rate of the single photon detector can reach 0.1-5Mcps, which is far higher than the dead time of 200-5000ns, so that a stacking effect is caused, namely photon arrival time is delayed, the trailing edge of a waveform is flattened, and the peak value is reduced, so that the absorption depth is systematically underestimated. The two distortions are coupled together, so that the traditional linear inversion error based on the beer-lambert law is greatly increased. At present, the engineering world commonly adopts a multi-point calibration strategy, namely a plurality of known concentration points are prepared in a constant-temperature closed pool, absorption waveforms are measured one by one at the stable temperature of a laboratory, and then a concentration-absorption area experience curve is established through polynomial or neural network fitting, but the method has four pain points, namely (1) the workload is large, the time cost is high for one-time complete calibration, the calibration is required to be carried out again every time a batch of lasers or optical fiber couplers are replaced, and (2) a temperature blind area is formed, namely the field temperature can be measured in the following stepsThe temperature of 20 ℃ to 50 ℃ is fluctuated, and the experimental calibration is usually carried out under the room temperature condition, (3) the concentration coverage is sparse, the actual leakage can be from tens ppm.m to tens of thousands ppm.m, the calibration point cannot be exhausted, the interpolation error is difficult to estimate, and (4) the migration cannot be carried out, the absorption section difference of different gases (CH 4、CO2、H2 S and the like) is huge, one set of calibration curve can only correspond to one gas, and the universality of equipment is severely limited. Therefore, there is an urgent need to develop a new calibration and inversion method, which can fundamentally overcome the limitations of the multi-point empirical calibration. Disclosure of Invention The invention provides a calibration and inversion method for single-photon laser radar gas detection, which is used for solving the technical problems of large calibration workload, poor field environment adaptability and limited concentration coverage in the prior art. In one aspect, the invention provides a calibration and inversion method for single-photon lidar gas detection, comprising: acquiring time domain photon counting data of the single-photon laser radar under the condition of no target gas absorption and a scanning time-frequency characteristic curve of a laser light source in the single-photon laser radar; Performing dead time correction processing on the time domain photon counting data to obtain a time domain instrument response function; Based on the time domain instrument response function and the scanning time-frequency characteristic curve, time-frequency mapping processing is adopted to obtain a frequency domain instrument response funct