Single-photon laser radar capable of simultaneously detecting leakage of various gases

Abstract

The invention discloses a single-photon laser radar for simultaneously detecting leakage of various gases. The single-photon laser radar comprises a multi-channel waveform generator, a plurality of continuous light source modules, a coupler, a multimode optical fiber circulator and a telescope which are connected in sequence, wherein the multimode optical fiber circulator is connected with the single-photon detector, and the single-photon detector is connected with the computer; the scanning starting time of the plurality of continuous light sources is staggered in the time domain, so that the absorption lines of a plurality of gases are separated in the time domain, and the simultaneous detection of a plurality of flammable, explosive, toxic and harmful gases is realized; the method has the effect of strong anti-interference capability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser radar, in particular to a single-photon laser radar for simultaneously detecting multiple gas leaks. BACKGROUND

[0002] Currently, the multiple gas leak detection technology can be divided into passive detection and active detection according to whether a light source is actively emitted. Passive detection includes passive infrared imaging (OGI), passive remote sensing Fourier transform infrared spectroscopy (RS-FTIR) and spectral imaging technology. These methods utilize the infrared radiation characteristics of the gas or the ambient background light, and can achieve simultaneous monitoring of multiple gases. However, passive detection technology faces challenges in achieving all-weather continuous monitoring due to environmental light interference. The working principle of active detection is to emit specific wavelengths related to gas absorption, and to calculate the gas concentration according to the degree of laser intensity absorption by the gas. Currently, integrating multiple different wavelength light sources and detectors is the main method for multiple gas leak detection. However, the multi-detector system increases the complexity of the system, especially in long-distance gas detection, which requires high-sensitivity detectors, increasing the system cost. SUMMARY

[0003] The purpose of the present application is to provide a single-photon laser radar for simultaneously detecting multiple gas leaks, achieving high sensitivity, non-contact, and simultaneous real-time detection of multiple components to solve the problems in the background technology.

[0004] The technical scheme of the present application is a single-photon laser radar for simultaneously detecting multiple gas leaks, comprising a multi-channel waveform generator, multiple continuous light source modules, a coupler, a multimode fiber ring, and a telescope connected in sequence. The multimode fiber ring is connected to a single-photon detector, and the single-photon detector is connected to a computer. The scanning start times of the multiple continuous light sources are staggered in the time domain, so that the absorption lines of the multiple gases are separated in the time domain, achieving simultaneous detection of multiple flammable, explosive, toxic, and harmful gases.

[0005] Further, in the multiple continuous light source modules, each light source module has a different central wavelength. The multi-channel waveform generator is used to provide multiple non-synchronous trigger signals to drive each continuous light source with a different central wavelength to work in a wavelength scanning state.

[0006] Further, the coupler is an Xx1 coupler with a single-mode fiber input and a multi-mode fiber output, used to couple multiple wavelengths of laser light into a single multi-mode fiber.

[0007] Further, the multi-mode fiber circulator is used to transmit the laser signal; the telescope is used to collimate the outgoing laser into the atmosphere and receive the backscattered echo signal from the non-cooperative target; the single photon detector is used to detect the echo signal and obtain the photon counting curve; and the computer is used to process the photon counting curve and obtain the gas type and the path integral concentration of the gas;

[0008] Further, the trigger signals provided by the multi-channel waveform generator have different time delays, so that the frequency scanning start times of the continuous light sources are staggered in the time domain; when there is no gas absorption, the photon counting curve is flat; when there is single gas absorption, the photon counting curve has a single absorption peak in the scanning period of the corresponding light source; and when there is multi-component gas absorption, the absorption peaks of each gas are separated in the time domain, and the photon counting curve has multiple independent absorption peaks, thereby realizing simultaneous detection of multi-component gas.

[0009] Further, the gas concentration detection method is as follows: first, all the continuous light sources are turned on at the same time to qualitatively identify the gas type. Specifically, all the continuous light sources are turned on at the same time, and the total laser power corresponding to the saturation of the single photon detector counting rate is set as P, and the outgoing power of each continuous light source is P / X, where X is the number of light sources. The backscattered echo signal after multi-component gas absorption is subjected to Voigt multi-peak fitting to separate the overlapping gas absorption lines, and the number and type of the leaked gases are determined according to the positions of the absorption lines in the time domain; and (2) the identified gases are detected one by one. Specifically, the continuous light sources corresponding to the identified leaked gases are turned off, and the outgoing power of the continuous light source corresponding to the to-be-detected gas is increased to P, the absorption spectrum of the single gas is scanned at a high signal-to-noise ratio, the Voigt line fitting is performed on the absorption spectrum, and the area method is used to calculate the path integral concentration of the gas.

[0010] Further, the multi-peak Voigt fitting function V mix The formula is as follows:

[0011]

[0012] wherein V n represents the Voigt fitting function of different gases, and the formula is as follows:

[0013]

[0014] wherein x=(4ln2) 1 / 2 (f-f0) / ω G , y=(ln2) 1 / 2 ω L / ω G ; A is the integral area after Voigt fitting, f0 is the center frequency, ω L =2Pγ0(T0 / T)nair Lorentzian full width at half maximum, ω G = f0(8kTln2 / mc 2 ) 1 / 2 is a Gaussian full width at half maximum; wherein, P is a gas pressure, γ0 is a Lorentzian full width at half maximum of broadening at one atmosphere, T0 = 296 K, n air is a temperature exponent of the air broadening full width at half maximum, γ0 and n air are obtained from the corresponding parameter values of the to-be-detected gas in the HITRAN database according to the atmospheric environment parameters (the gas pressure P and the measured temperature T) ; k = 1.38 x 10 -23 J / K is the Boltzmann constant, m is the molecular weight, c = 2.998 x 10 8 m / s is the speed of light.

[0015] Further, the flammable, explosive, toxic and harmful gases include at least two of methane CH4, hydrogen H2, carbon monoxide CO, hydrogen sulfide H2S, acetylene C2H2, hydrogen fluoride HF, hydrogen cyanide HCN, ammonia NH3 and the like.

[0016] The operation method of the single-photon laser radar for simultaneously detecting multiple gas leaks, provided by the application, comprises the following steps:

[0017] (1) A non-synchronous trigger signal is obtained through a multi-channel waveform generator to drive a continuous light source module to perform wavelength scanning;

[0018] (2) A plurality of wavelength lasers are coupled to a multimode fiber circulator through a coupler and are emitted through a telescope;

[0019] (3) The telescope simultaneously receives a backscattering echo signal, and a photon counting curve is obtained by a single-photon detector;

[0020] (4) The photon counting curve is processed by a computer, a gas type is qualitatively identified through multi-peak Voigt fitting, and a concentration is quantitatively calculated through a power-enhanced individual scan.

[0021] Beneficial effects: Compared with the prior art, the application has the following remarkable advantages: The application realizes high sensitivity, non-contact, multi-component simultaneous detection, and has the effect of strong anti-interference capability. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a structural schematic diagram of the application;

[0023] Figure 2 is a timing structure diagram of the application;

[0024] Figure 3 is a gas concentration detection mode of the application. DETAILED DESCRIPTION

[0025] The technical solutions of the present application are further described below with reference to the accompanying drawings.

[0026] As Figure 1 shown, the embodiment of the present application provides a single-photon laser radar for simultaneously detecting leakage of multiple gases, comprising: a multi-channel waveform generator 1, multiple continuous light source modules 2, a coupler 3, a multimode fiber ring 4, a telescope 5 connected in sequence; wherein the multimode fiber ring 4 is connected to a single-photon detector 6, and the single-photon detector 6 is connected to a computer 7; the multi-channel waveform generator 1 provides multiple non-synchronous trigger signals, and the multiple continuous light source modules 2 are used to drive each continuous light source with different center wavelengths to work in a wavelength scanning state. Multiple lasers with different wavelengths enter the coupler 3 through a single-mode fiber and are coupled into a multimode fiber, and are delivered to the telescope 5 through the ring 4 and collimated out of the atmosphere; the telescope 5 receives the backscattered echo signal of the detection light after being absorbed by the gas and scattered by the non-cooperative target, and inputs it to the single-photon detector through the ring for direct detection, obtaining a photon counting curve with gas concentration information; finally, the computer processes the data to obtain the path integral concentration of the gas.

[0027] Among them, the multi-channel waveform generator 1 is used to provide multiple non-synchronous trigger signals; in the multiple continuous light source modules 2, each light source module has a different center wavelength to drive each continuous light source with a different center wavelength to work in a wavelength scanning state. The coupler 3 is an X×1 coupler, the input end is a single-mode fiber, and the output end is a multimode fiber, which is used to couple multiple wavelengths of laser into a multimode fiber. The multimode fiber ring 4 is used to deliver the laser signal; the telescope 5 is used to collimate the laser out of the atmosphere and receive the backscattered echo signal; the single-photon detector 6 is used to detect the echo signal and obtain a photon counting curve; the computer 7 is used to process the photon counting curve to obtain the type of gas and the path integral concentration of the gas.

[0028] As Figure 2 shown, the trigger signals provided by the channel waveform generator 1 have different time delays, so that the frequency scanning start times of each continuous light source are staggered in the time domain; when there is no gas absorption, the photon counting curve is flatly distributed; when there is single gas absorption, the photon counting curve has a single absorption peak in the scanning period of the corresponding light source; when there is multiple gas absorption, the absorption peaks of each gas are separated in the time domain, and the photon counting curve presents multiple independent absorption peaks, realizing the simultaneous detection of multi-component gas.

[0029] A multi-channel waveform generator provides trigger signals with different time delays for each continuous light source, as Figure 2 (a) shown. Under the modulation of asynchronous trigger signals, the frequency scanning start times of each continuous light source are staggered in the time domain, as Figure 2(b) shown. When there is no gas absorption, the photon counting result is as shown in Figure 2 (c); when there is single gas absorption, assuming that the gas absorption corresponding to the continuous light source L1, the photon counting result is as shown in Figure 2 (d); when there is multiple gas absorption, assuming that there are three kinds of gas, the absorption lines of different gases scanned by each continuous light source are separated in the time domain, and the photon counting result is as shown in Figure 2 (e), wherein the solid line is the mixed result of the three kinds of gas, and the dashed line, the dash-dotted line and the dotted line correspond to the absorption results of the three kinds of gas respectively. Under this special timing structure, multiple gases can be detected at the same time, and only one detector is needed, which reduces the complexity and cost of the system.

[0030] As shown in Figure 3 , the gas concentration detection method is as follows: first, qualitative identification of gas types by multi-peak Voigt fitting: all continuous light sources are turned on at the same time, and the total laser power corresponding to the saturation of the single-photon detector counting rate is set as P, the output power of each continuous light source is P / X, wherein X is the number of light sources, the Voigt line function is used to perform multi-peak fitting on the detected spectrum, separate the overlapping gas absorption lines, and confirm the gas leakage type according to the position of the absorption line in the time domain; then, the concentration is calculated quantitatively by power boosting individual scanning: turn off the other light sources except the continuous light source corresponding to the confirmed leakage gas, and boost the output power of the continuous light source corresponding to the gas to be measured to P, perform high signal-to-noise ratio scanning on the single gas absorption spectrum, and calculate the path integral concentration of the gas by the area method of Voigt line fitting. The multi-peak Voigt fitting function V mix is as follows:

[0031]

[0032] wherein V n represents the Voigt fitting function of different gases, and the formula is as follows:

[0033]

[0034] wherein x=(4ln2) 1 / 2 (f-f0) / ω G , y=(ln2) 1 / 2 ω L / ω G ; A is the integral area after Voigt fitting, f0 is the center frequency, ω L =2Pγ0(T0 / T) nair is the full width at half maximum of Lorentz, ω G =f0(8kTln2 / mc 2 ) 1 / 2wherein P is the gas pressure, γ0 is the Lorentzian half-width at one atmosphere, T0 = 296 K, n air is the temperature exponent for the air-broadened half-width, γ0 and n air are the corresponding parameter values for the gas under test, which can be obtained from the HITRAN database according to the atmospheric environmental parameters (the gas pressure P and the measured temperature T) ; k = 1.38 x 10 -23 J / K is the Boltzmann constant, m is the molecular weight, c = 2.998 x 10 8 m / s is the speed of light.

[0035] The flammable, explosive, toxic and harmful gases referred to in the present application include at least two of methane CH4, hydrogen H2, carbon monoxide CO, hydrogen sulfide H2S, acetylene C2H2, hydrogen fluoride HF, hydrogen cyanide HCN, ammonia NH3 and the like.

Claims

1. A single-photon laser radar for detecting multiple gas leaks simultaneously, characterized in that: include: A multi-channel waveform generator (1), a plurality of continuous light source modules (2), a coupler (3), a multimode optical fiber circulator (4), and a telescope (5) are connected in sequence; wherein the multimode optical fiber circulator (4) is connected to a single photon detector (6), and the single photon detector (6) is connected to a computer (7); the scanning start times of the plurality of continuous light sources are staggered in the time domain, so that the absorption lines of the plurality of gases are separated in the time domain, thereby realizing the simultaneous detection of a plurality of flammable, explosive, toxic and harmful gases.

2. The single-photon laser radar for simultaneously detecting multiple gas leaks according to claim 1, characterized in that: Among the multiple continuous light source modules (2), each light source module has a different central wavelength and corresponds to a gas; the multi-channel waveform generator (1) is used to provide multiple asynchronous trigger signals to drive the continuous light sources with different central wavelengths to operate in a wavelength scanning state.

3. The single-photon laser radar for simultaneously detecting multiple gas leaks according to claim 1, characterized in that: The coupler (3) is an X×1 coupler, the input end of which is a single-mode optical fiber and the output end of which is a multi-mode optical fiber, and is used for coupling lasers of multiple wavelengths into one multi-mode optical fiber.

4. The single-photon laser radar for simultaneously detecting multiple gas leaks according to claim 1, characterized in that: The multimode optical fiber circulator (4) is used to transmit laser signals; the telescope (5) is used to collimate the emitted laser into the atmosphere and receive the echo signal backscattered by the non-cooperative target; the single photon detector (6) is used to detect the echo signal and obtain a photon counting curve; the computer (7) is used to process the photon counting curve and calculate the gas path integrated concentration.

5. The single-photon laser radar for simultaneously detecting multiple gas leaks according to claim 1, characterized in that: The trigger signals provided by the multi-channel waveform generator (1) have different delays, so that the frequency scanning start times of each continuous light source are staggered in the time domain; when there is no gas absorption, the photon counting curve is flatly distributed; when there is a single gas absorption, the photon counting curve has an absorption peak in the scanning period of the corresponding light source; when there are multiple gases absorption, the absorption peaks of each gas are separated in the time domain, and the photon counting curve presents multiple independent absorption peaks, thereby realizing the simultaneous detection of multi-component gases.

6. The single-photon laser radar for simultaneously detecting multiple gas leaks according to claim 1, characterized in that: The specific method of gas concentration detection is as follows: (1) Turn on all continuous light sources at the same time to qualitatively identify the type of gas. Specifically, turn on all continuous light sources at the same time, set the total laser power corresponding to the saturation of the single-photon detector count rate to P, and the output power of each continuous light source to P / X, where X is the number of light sources. Perform Voigt multi-peak fitting on the echo signals after absorption of multiple gases, separate the overlapping gas absorption lines, and confirm the number and type of gas leakage based on the position of the absorption lines in the time domain; (2) Perform separate detection on the identified gases in turn. Specifically, turn off all light sources except the continuous light source corresponding to the confirmed leaked gas, increase the output power of the continuous light source corresponding to the gas to be tested to P, perform high signal-to-noise ratio scanning on the absorption spectrum of the individual gas, perform Voigt linear fitting on the absorption spectrum, and use the area method to calculate the path integrated concentration of the gas.

7. The single-photon laser radar for simultaneously detecting multiple gas leaks according to claim 6, characterized in that: Multi-peak Voigt fitting function V mix The formula is as follows: Where V n The Voigt fitting function representing different gases is: where x = (4ln²) 1 / 2 (f-f0) / ω G , y=(ln2) 1 / 2 ω L / ω G ; A is the integral area after Voigt fitting, f0 is the center frequency, ω L =2Pγ0(T0 / T) nair is the Lorentz full width at half maximum, ω G =f0(8kTln2 / mc 2 ) 1 / 2 is the Gaussian full width at half maximum; where P is the gas pressure, γ0 is the Lorentzian half width at half maximum broadened at atmospheric pressure, T0 = 296K, n air is the temperature exponent of the half-width at half-maximum of the air, γ0 and n air The corresponding parameter values ​​of the gas to be measured can be obtained from the HITRAN database according to the atmospheric environmental parameters (pressure P and measured temperature T); k = 1.38 × 10 -23 J / K is the Boltzmann constant, m is the molecular weight, and c = 2.998 × 10 8 m / s is the speed of light.

8. The single-photon laser radar for simultaneously detecting multiple gas leaks according to claim 1, characterized in that: The flammable, explosive, toxic and harmful gases include at least two of methane CH4, hydrogen H2, carbon monoxide CO, hydrogen sulfide H2S, acetylene C2H2, hydrogen fluoride HF, hydrogen cyanide HCN, ammonia NH3 and the like.

9. A method for operating a single-photon laser radar for simultaneously detecting multiple gas leaks, characterized in that: Including steps: (1) Obtaining asynchronous trigger signals through a multi-channel waveform generator to drive the continuous light source module to perform wavelength scanning; (2) Using a coupler to couple multiple wavelength lasers to a multimode fiber circulator, and then emitting through a telescope; (3) The telescope simultaneously receives the backscattered echo signal and obtains the photon counting curve by the single photon detector; (4) The photon counting curve is processed by computer, and the gas species are first qualitatively identified by multi-peak Voigt fitting, and then the concentration is quantitatively calculated by combining power-boosted single scanning with the area method.

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