CN115015966A - Gas detection laser radar based on wide-spectrum light source - Google Patents

Abstract

The application provides a gas detection lidar based on a broad-spectrum light source, and relates to the technical field of lidar. The gas detection lidar uses a broad-spectrum laser as a laser source, and filters out lasers with multiple wavelengths through a multi-channel filter for gas detection. When receiving, the wavelength division multiplexer is used for demultiplexing of multiple wavelengths and simultaneous detection of multiple wavelengths to obtain distance-resolved and spectral-resolved absorption lines of the gas to be tested. The invention uses optical communication devices to complete wide-spectrum atmospheric gas composition remote sensing, and has the following advantages: firstly, multiple single-frequency lasers are not required, and the broadband light source can further increase the output power and reduce the system cost; secondly, the return of multiple wavelengths The wave signal is detected synchronously, and the absorption spectrum of the gas to be measured is obtained with high temporal and spatial resolution; finally, the all-fiber system is conducive to integration and miniaturization.

Description

A Gas Detection Lidar Based on Broad Spectrum Light Source

technical field

The invention relates to the field of laser radar, and more particularly, to a gas detection laser radar based on a broad-spectrum light source.

Background technique

Remote sensing of atmospheric gas composition is of great significance to meteorological and climate research, pollutant monitoring and atmospheric photochemical reaction research.

At present, the measurement of atmospheric gas composition mainly relies on in-situ measurement equipment and lidar. Although in-situ measurement technology can obtain high-precision various gas compositions, it cannot obtain gas composition measurement of three-dimensional spatial distribution, and it is difficult to locate the source of gas pollution and gas. Lidar is an effective way to realize 3D remote sensing of atmospheric gas composition.

The inventor of the present invention found that the gas detection laser radar mainly adopts differential absorption laser radar, path integral differential absorption laser radar and hyperspectral resolution laser radar. Differential absorption lidar uses two wavelengths of laser light, one is located at the position where the absorption cross-section of the gas to be measured is strong, and the other is located at the position where the absorption cross-section of the gas to be measured is weak. The laser used for differential absorption lidar needs to have narrow linewidth and high wavelength stability, and different lasers are required for different gases to be measured, so the cost of differential absorption lidar system is high. Based on the wavelength scanning lidar with hyperspectral resolution, a variety of gas absorption spectra can be obtained by scanning the spectrum. However, it requires real-time laser wavelength locking and calibration during the scanning process. The system is complex and the scanning process is time-consuming, resulting in low time resolution.

SUMMARY OF THE INVENTION

(1) Technical problems solved

The object of the present invention is to provide a gas detection laser radar based on a broad-spectrum light source, which is used to solve the problem that the existing laser radar needs real-time laser wavelength locking and calibration during the scanning process, and the system is complex and the scanning process is time-consuming, resulting in low time resolution. question.

(2) Technical solutions

In order to achieve the above purpose, the present invention is achieved through the following technical solutions: a gas detection laser radar based on a broad-spectrum light source, characterized in that it includes: a broad-spectrum light source, a multi-channel filter, a pulse generation and power amplification module, a laser beam Transceiver module, demultiplexing module, multi-channel detection module, data acquisition module and data processing module;

Wherein, the broad-spectrum light source is used to emit broad-spectrum laser light;

The multi-channel filter is used to filter out a plurality of laser signals of different frequencies from the broad-spectrum laser emitted by the broad-spectrum light source, and the plurality of different frequencies correspond to different positions of the absorption curve of the gas to be measured; wherein, each filtered frequency corresponds to The full width at half maximum of the curve is less than the preset threshold; the gas to be tested contains one or more gases;

The pulse generating and power amplifying module is used for chopping the continuous light output by the broad-spectrum light source into pulsed light and amplifying the power of the pulsed light through a laser amplifier;

The laser beam transceiver module is used for outputting amplified laser pulses to the gas to be measured, and receiving backscattered signals of the laser in the gas to be measured;

The demultiplexing module is used for demultiplexing the laser backscattered signals of multiple frequencies into corresponding multiple optical fiber signal channels, and different optical fiber signal channels correspond to different signal frequencies;

The multi-channel detection module includes a plurality of detection channels, which are used for detecting signals in the plurality of optical fiber signal channels demultiplexed by the demultiplexing module, and outputting corresponding electrical signals;

The data acquisition module is used to collect electrical signals output by the multi-channel detection module;

The data processing module is used for processing the echo signals of multiple frequencies collected by the data acquisition module, inverting the absorption spectrum of the gas to be measured at different distances, and calculating the gas concentration at different distances.

Further, the broad-spectrum light source is a broad-spectrum light source in the ultraviolet to infrared wavelength band.

Further, the multi-channel filter is a Fabry-Perot interferometer; the preset threshold is 100 MHz.

Further, the laser beam transceiver module includes a circulator and a telescope, the circulator is used to emit the amplified laser pulses to the telescope, and the circulator is also used to receive the gas to be measured back by the telescope. The backscattered signal is transmitted to the demultiplexing module; the telescope is used to emit the laser beam to the gas to be tested and receive the backscattered signal of the gas to be tested.

Further, the demultiplexing module is a WDM wavelength division multiplexer or a dispersion grating.

Further, the de-wavelength division multiplexing module includes a plurality of output terminals, the multi-channel detection module includes a plurality of corresponding detection channels, and each detection channel is used to detect a corresponding output end of the de-wavelength division multiplexing module. signal of.

Further, the multi-channel detection module includes a multi-channel photodetector corresponding to the output band of the broad-spectrum light source.

Further, the multi-channel detection module includes a plurality of photodetectors.

Further, the photodetector is a photomultiplier tube, a silicon detector, an indium gallium arsenide detector or a mercury cadmium telluride detector.

Further, the data processing module uses the Lorentz curve fitting algorithm to invert the concentration of the gas to be measured, and performs Lorentz curve fitting on the multi-channel echo signal to obtain the area of the absorption curve of the gas to be measured. Calculate the concentration of the gas to be measured.

Further, the data processing module includes a nonlinear fitting unit and a gas concentration calculation unit;

The nonlinear fitting unit is configured to obtain absorption spectra at different distances according to the echo signals of multiple frequencies collected by the data acquisition module, and perform nonlinear fitting on the absorption spectra to obtain a fitting curve;

The gas concentration calculation unit is configured to calculate the area of the fitting curve, and calculate the concentration of the gas to be measured according to the area.

Further, performing nonlinear fitting on the absorption spectrum, including:

applying Lorentzian curve fitting to the absorption spectrum;

If the absorption spectrum contains one absorption peak, then fitting the absorption spectrum with a single-peak Lorentzian curve;

If the absorption spectrum contains multiple absorption peaks, a multi-peak Lorentzian curve fitting is used for the absorption spectrum.

(3) Beneficial effects

(1) The present invention is a gas detection laser radar based on a wide-spectrum light source. By using a wide-spectrum light source, it overcomes the strong stimulated Brillouin scattering effect caused by the narrow linewidth light source required by the traditional laser radar, and further reduces the impact on the laser beam. The output power is limited, so broad-spectrum light sources can achieve significant improvements in lidar power and signal-to-noise ratio. The invention adopts a broad-spectrum light source and a multi-channel filter module, does not need to configure multiple light sources, has low cost, covers a wide spectrum range, and can detect multiple gases at the same time. In addition, compared with the narrow linewidth light source of the existing laser radar, the present invention adopts a wide spectrum light source with low cost and has a great price advantage.

(2) The present invention is a gas detection laser radar based on a broad-spectrum light source. By using a multi-channel filter to filter out a plurality of lasers of different frequencies for detection, it can realize the simultaneous detection of gas spectra of various components. The method of the present invention is adopted. , only one measurement, no need to scan the spectrum, no real-time laser wavelength locking and calibration, which greatly simplifies the complexity of the simultaneous detection system for multiple gas components, fast measurement speed, less time-consuming, and can achieve quasi-real-time measurement , significantly improving the temporal resolution.

(3) The present invention is a gas detection laser radar based on a broad-spectrum light source. The demultiplexer of the present invention transmits atmospheric echo signals of multiple frequencies to a multi-channel detector for signal detection, thereby achieving high temporal and spatial resolution. Detection of gas spectra at rates.

(4) The present invention is a gas detection laser radar based on a broad-spectrum light source. The data processing module of the present invention uses the Lorentz curve fitting algorithm to invert the concentration of the gas to be measured, and performs the Lorentz curve on the multi-channel echo signals. Fitting to obtain the area of the absorption curve of the gas to be measured, and calculating the concentration of the gas to be measured according to the area, higher detection accuracy can be obtained.

Description of drawings

1 is a schematic structural diagram of a gas detection lidar based on a broad-spectrum light source provided by an embodiment of the present invention;

FIG. 2 is a spectrogram of a broad-spectrum light source at a certain position provided by an embodiment of the present invention;

3 is a spectrogram of a light source at a certain position provided by an embodiment of the present invention after being subjected to a multi-channel filter;

4 is an atmospheric gas absorption line at a certain position provided by an embodiment of the present invention;

FIG. 5 is radar echo signals of different wavelengths provided by an embodiment of the present invention;

6 is a transmittance curve of each channel of a demultiplexer provided by an embodiment of the present invention;

Fig. 7 is the gas absorption intensity of the gas to be detected by multi-wavelength detection after data processing at a certain position provided by the embodiment of the present invention, and the gas absorption spectrum of nonlinear fitting;

FIG. 8 is an absorption spectrum obtained by measurement at different distances when the gas to be measured contains two gases in an embodiment of the present invention.

FIG. 9 is a fitting curve obtained by fitting the absorption spectra at different distances by a bimodal Lorentzian curve when the gas to be tested contains two gases in the embodiment of the present invention.

Among them, 1. Broad-spectrum light source; 2. Multi-channel filter; 3. Pulse generation and power amplification module; 4. Power amplification module; 20. Laser beam transceiver module; 5. Circulator; 6. Telescope; 7. Dewave Multiplexing module; 8. Multi-channel detection module; 9. Data acquisition module; 10. Data processing module.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example

Referring to FIG. 1, FIG. 1 is a schematic structural diagram of a gas detection lidar based on a broad-spectrum light source provided by an embodiment of the present invention. The gas detection lidar includes: a broad-spectrum light source 1, a multi-channel filter 2, a pulse generator and a Power amplification module 3 , power amplification module 4 , laser beam transceiver module 20 , wavelength division multiplexing module 7 , multi-channel detection module 8 , data acquisition module 9 and data processing module 10 .

The output end of the broad-spectrum light source is connected with the output end of the multi-channel filter, the output end of the multi-channel filter is connected with the input end of the pulse generation and power amplifying module, and the output end of the power amplifying module is connected with the input end of the laser beam transceiver module The output end of the laser beam transceiver module is connected with the input end of the demultiplexing module, and the output end of the demultiplexing module is connected with the input end of the multi-channel detection module; the above connections are all optical fiber connections. The multi-channel detection module, the data acquisition module and the data processing module are connected in sequence.

Wherein, the broad-spectrum light source 1 is used for emitting broad-spectrum laser light. For the narrow linewidth light source required by non-traditional lidar, the narrower the linewidth, the stronger the stimulated Brillouin scattering effect, thus limiting the output power of the laser. The broad-spectrum light source has low cost, wide spectral linewidth, and weak stimulated Brillouin scattering effect, so the power of the light source can be increased.

In one embodiment, the broad-spectrum light source 1 is a broad-spectrum light source in the ultraviolet to infrared wavelength band, so as to realize the coverage of various gas absorption lines and improve the gas detection capability of the lidar.

In one embodiment, the broad-spectrum light source 1 is an ASE spontaneous emission light source or a white light source. Among them, the ASE spontaneous emission light source has the advantages of low cost and wide spectral coverage.

The broad-spectrum light source selects laser light in the wavelength range of 1 μm to 2 μm with low loss in the optical fiber, preferably in the 1.5 μm wavelength band. This band is eye-safe and has low transmission loss.

The multi-channel filter 2 is used to filter out a plurality of laser signals of different frequencies from the broad-spectrum light source, and the plurality of different frequencies correspond to different positions of the absorption curve of the gas to be measured; The full width at half maximum is smaller than the preset threshold. The gas to be measured contains one or more gases.

Further, the multi-channel filtering

The device is a Fabry-Perot interferometer; the preset threshold is 100MHz. Since the present invention needs to measure multiple gases simultaneously through one gas absorption curve, if the full width at half maximum of the measured gas absorption curve corresponding to each filtered frequency is too large, the two gases cannot be distinguished. The inventor of the present invention has found through research that when the threshold value is 100 MHz, different gas components can be distinguished by the absorption curve of the gas to be measured.

The Fabry–Pérot interferometer (FPI) is a multi-beam interferometer composed of two parallel glass plates. The opposing inner surfaces of two of the glass sheets are highly reflective.

For the Fabry-Perot etalon, the significant change in transmittance with wavelength is due to the interference of multiple reflected light between the two reflectors. When the transmitted light is in phase, they interfere constructively, corresponding to the peak of the etalon transmittance; when the transmitted light is out of phase, it corresponds to the minimum value of the transmittance. Whether multiple reflections are in phase with each other depends on the frequency of the incident light, the angle of refraction of the light propagating within the etalon, the thickness of the etalon and the refractive index of the material used.

，在不考虑相移时的相位差为The optical path difference between two adjacent reflected beams in the Fabry-Perot etalon

, the phase difference without considering the phase shift is

为入射光中心波长；

为入射角；Among them, n is the refractive index in the standard cavity; l is the cavity length of the etalon,

is the central wavelength of the incident light;

is the angle of incidence;

In addition, the reflectivity of the internal interface is R, the transmittance function Te of the _etalon is given by the following formula

When the optical path difference between two adjacent beams of light is an integer multiple of the wavelength, the transmittance function has a maximum value of 1. In the case where the medium does not absorb light, the reflectivity _Re of the etalon satisfies

，也就是光程差为波长的半奇数倍时透射率函数有最小值，此时对应着反射率的最大值R_max when

, that is, when the optical path difference is a half-odd multiple of the wavelength, the transmittance function has a minimum value, which corresponds to the maximum value R _max of the reflectivity.

As a function of transmittance, the wavelength separation between two adjacent transmission peaks is called the free spectral distance (FSR) of the etalon and is given by:

表示标准具的自由光谱间距，

是最近峰值的中心波长。in,

represents the free spectral spacing of the etalon,

is the center wavelength of the nearest peak.

Since the invention needs to measure multiple gases simultaneously on one absorption line, there are special requirements for the free spectral spacing of the multi-channel filter. The free spectral spacing needs to be less than 6.25 GHz, the full width at half maximum of the transmittance curve needs to be less than 100 MHz, If the height and full width are too large, it cannot be used for the detection of gas absorption lines.

FPI can generate a transmittance curve with a free spectral spacing of 6.25GHz and a full width at half maximum less than 100MHz, further completes the multi-channel filtering of the broad-spectrum spectrum, and generates beams of multiple frequencies for broad-spectrum gas detection.

Therefore, the multi-channel filter is a Fabry-Perot interferometer; the preset threshold is 100 MHz.

The pulse generating and power amplifying module is used for chopping the continuous light output from the broad-spectrum light source into pulsed light and amplifying the power of the pulsed light through a laser amplifier.

The pulse generation and power amplification module includes a pulse generator 3 and a power amplifier 4 .

The pulse generator 3 is used to chop the broad-spectrum light source into pulsed light. The pulse generators are electro-optical modulator EOM, acousto-optical modulator AOM and so on.

The power amplifier 4 is used for power amplification of pulsed light; the power amplifier is preferably a fiber laser amplifier, such as an erbium-doped fiber amplifier EDFA and the like.

The laser beam transceiver module 20 is used for outputting the amplified laser pulses to the atmosphere, and receiving the backscattered signals of the laser light in the atmosphere.

The demultiplexing module 7 is used for demultiplexing the laser backscattered signals of multiple frequencies into corresponding multiple optical fiber signal channels. Different optical fiber signal channels correspond to different signal frequencies.

Further, the demultiplexing module 7 is a WDM wavelength division multiplexer or a dispersion grating. WDM (WavelengthDivision Multiplexing) is a wavelength division multiplexer.

The multi-channel detection module 8 includes a plurality of detection channels, which are used to detect the echo signals in the multiple optical fiber signal channels after demultiplexing, and output corresponding electrical signals; the echo signals of different frequencies are obtained by different detection channels .

The input end of the demultiplexing module 7 is connected to the output end of the laser beam transceiver module 20. The output end of the demultiplexing module 7 includes a plurality of optical fiber channels, and the plurality of optical fiber channels of the demultiplexing module 7 are respectively Correspondingly connected with multiple detection channels.

In one embodiment, the de-wavelength division multiplexing module includes a plurality of output terminals, the multi-channel detection module includes a plurality of corresponding detection channels, and each detection channel is used for detecting a corresponding de-wavelength division multiplexing module output signal.

The multi-channel detection module includes a multi-channel photodetector corresponding to the output band of the broad-spectrum light source. In this way, only one multi-channel detector is needed to realize multi-channel detection, the system structure is simplified, and the system cost and volume are saved.

In another embodiment, the multi-channel detection module includes a plurality of photodetectors.

The photodetectors are photomultiplier tubes, silicon detectors, indium gallium arsenide detectors or mercury cadmium telluride detectors.

The data collection module 9 is used to collect the electrical signals output by the multi-channel detection module 8 .

The data processing module 10 is used for processing echo signals of multiple frequencies, inverting absorption spectra of the gas to be measured at different distances, and calculating gas concentrations at different distances.

Further, the data processing module uses the Lorentz curve fitting algorithm to invert the concentration of the gas to be measured, and performs Lorentz curve fitting on the multi-channel echo signal to obtain the area of the absorption curve of the gas to be measured. To calculate the concentration of the gas to be detected, by using the algorithm of the present invention, higher gas detection accuracy can be obtained simply and quickly.

Further, the laser beam transceiver module 20 includes a circulator 5 and a telescope 6, and the circulator 5 is used to emit the amplified laser pulses to the telescope, and is also used to receive the atmosphere returned by the telescope 6. The backscattered signal is transmitted to the demultiplexing module 7; the telescope 6 is used to emit the laser beam into the atmosphere and receive the atmospheric backscattered signal.

Based on all the above embodiments of the present invention, the specific working principle thereof will be described below.

Referring to FIG. 2 , FIG. 2 is a spectrum diagram of a broad-spectrum light source at a certain position provided by an embodiment of the present invention.

As shown in FIG. 2 , it corresponds to point a in FIG. 1 and is located between the broad-spectrum light source 1 and the multi-channel filter 2 . FIG. 2 illustrates the spectrum of the broad-spectrum light source emitted by the broad-spectrum light source 1 .

Referring to FIG. 3 , it is a spectrogram of a light source at a certain position provided by an embodiment of the present invention after being subjected to a multi-channel filter.

As shown in Figure 3, it corresponds to point b in Figure 1 and is located between the multi-channel filter 2 and the pulse generation module 3. Figure 3 shows the spectrum of the broad-spectrum light source after filtering by the multi-channel filter. Here is an example of a free spectrum A Fabry-Perot interferometer with a spacing of 6.25 GHz is used as a multi-channel filter, and λ1, λ2, λ3, λ4, λ5, λ6 and λ7 are the central wavelengths of each channel filter, respectively.

Referring to FIG. 4 , FIG. 4 is an atmospheric gas absorption line at a certain position according to an embodiment of the present invention.

As shown in FIG. 4 , it corresponds to point c in FIG. 1 and is located in the atmosphere behind the laser beam transceiver module 20 . FIG. 4 illustrates the absorption spectrum of the gas to be measured.

Referring to FIG. 5 , FIG. 5 is a radar echo signal of different wavelengths provided by an embodiment of the present invention.

As shown in Figure 5, which corresponds to point d in Figure 1, it is located between the circulator 5 and the demultiplexing module 7, and the multi-channel filter 2 has filtered out 7 channels, and here it is shown that two of the central wavelengths are λ1 and the echo signal of the channel of λ4.

Referring to FIG. 6, FIG. 6 is a transmittance curve of each channel of a demultiplexer provided by an embodiment of the present invention.

As shown in Figure 6, it corresponds to point e in Figure 1, and is located in the demultiplexing module 7. The central wavelength and channel interval of each channel of the demultiplexing module correspond to the multi-channel filter, and the position of the central wavelength They are λ1, λ2, λ3, λ4, λ5, λ6 and λ7 respectively. The demultiplexing module 10 demultiplexes the echo signals of each wavelength into multiple fibers, and the demultiplexed multi-channel echo signals are multi-channel. The detection module 8 receives, and the electrical signal output by the detection module is sent to the data acquisition module 9 for collection.

Referring to FIG. 7 , FIG. 7 shows the multi-wavelength detection of the gas absorption intensity to be detected after data processing at a certain position, and the gas absorption spectrum of nonlinear fitting according to an embodiment of the present invention.

As shown in FIG. 7 , it corresponds to point f in FIG. 1 and is located in the data processing module 10. After obtaining the echo signals of each channel, the data processing module 10 processes and obtains the absorption coefficients of multiple wavelengths at each distance. , the absorption coefficients of 7 wavelengths at one distance are shown as circles in Figure 7. Further, by nonlinear fitting of the obtained multi-wavelength absorption coefficients, the absorption spectral line of the gas to be measured at the distance is obtained, and finally the absorption characteristics of the gas to be measured with spectral resolution, temporal resolution and spatial resolution are obtained.

Further, the data processing module uses the Lorentz curve fitting algorithm to invert the concentration of the gas to be measured, and performs Lorentz curve fitting on the multi-channel echo signal to obtain the area of the absorption curve of the gas to be measured. Calculate the concentration of the gas to be measured.

Specifically, the data processing module includes a nonlinear fitting unit and a gas concentration calculation unit;

The nonlinear fitting unit is configured to obtain absorption spectra at different distances according to the echo signals of multiple frequencies collected by the data acquisition module, and perform nonlinear fitting on the absorption spectra to obtain a fitting curve;

The gas concentration calculation unit is configured to calculate the area of the fitting curve, and calculate the concentration of the gas to be measured according to the area.

Specifically, since the concentration of the gas to be measured is determined by the partial pressure P, and the partial pressure satisfies the following formula:

Among them, A is the Lorentz line area of the absorption coefficient, P is the partial pressure of the gas to be measured, T is the temperature of the gas to be measured, T0 = 273.15 K, P0 = 100 kPa, n _L is the temperature of the gas to be measured at Line intensities at T0 and P0. By performing Lorentzian line fitting on the measured absorption coefficient, the area A can be obtained, and the partial pressure P can be further calculated to obtain the concentration of the gas to be measured.

In the present invention, the nonlinear fitting is preferably Lorentzian curve fitting.

Further, performing nonlinear fitting on the absorption spectrum, including:

applying Lorentzian curve fitting to the absorption spectrum;

If the absorption spectrum contains one absorption peak, then fitting the absorption spectrum with a single-peak Lorentzian curve;

If the absorption spectrum contains multiple absorption peaks, a multi-peak Lorentzian curve fitting is used for the absorption spectrum.

The multiple absorption peaks correspond to one or more gases in the gas to be measured; if the absorption spectrum contains N gas absorption peaks, the N peaks are fitted to the absorption spectrum, and the fitting of the gas corresponding to each absorption peak is obtained respectively. curve. Then calculate the concentration of each gas according to the fitted curve of each gas.

FIG. 7 is a fitting curve obtained by fitting a single-peak Lorentzian curve to the absorption spectra at different distances when the gas to be tested contains only one gas.

FIG. 8 shows absorption spectra obtained by measurement at different distances when the gas to be measured contains two gases.

FIG. 9 is a fitting curve obtained by using a bimodal Lorentzian curve to fit the absorption spectra at different distances when the gas to be tested contains two gases. When calculating the gas concentration, the two fitted curves are calculated separately to obtain the concentration of the two gases.

To sum up, the gas detection lidar based on the broad-spectrum light source provided by the present invention overcomes the strong stimulated Brillouin scattering effect caused by the use of the traditional lidar due to the requirement of a narrow-linewidth light source by using a broad-spectrum light source, In turn, the output power of the laser is limited, so the broad-spectrum light source can significantly improve the power and signal-to-noise ratio of the lidar. The invention adopts a broad-spectrum light source and a multi-channel filter module, does not need to configure multiple light sources, has low cost, covers a wide spectrum range, and can detect multiple gases at the same time.

The invention uses a multi-channel filter to filter out a plurality of lasers with different frequencies for detection. Since a plurality of different frequency components are located at different positions of the absorption line to be measured, simultaneous detection of gas spectra of various components can be realized. This method requires only one measurement, does not need to scan the spectrum, and does not require real-time laser wavelength locking and calibration, which greatly simplifies the complexity of the simultaneous detection system for multiple gas components. The measurement speed is fast, time-consuming, and accurate Real-time measurement with significantly improved temporal resolution.

The demultiplexer of the present invention transmits atmospheric echo signals of multiple frequencies to a multi-channel detector for signal detection, thereby completing gas spectrum detection with high temporal and spatial resolution.

Compared with the narrow linewidth light source of the existing laser radar, the present invention adopts the broad spectrum light source with low cost and has a great price advantage.

The optical fiber communication devices used in the present invention are mature, such as multi-channel filters and demultiplexers, to complete the wide-spectrum gas absorption spectrum detection. Compared with the traditional gas detection laser radar, the radar can not only obtain spectral resolution, but also obtain spatiotemporal resolution.

The data processing module of the present invention uses the Lorentz curve fitting algorithm to invert the concentration of the gas to be measured, performs Lorentz curve fitting on the multi-channel echo signal to obtain the area of the absorption curve of the gas to be measured, and calculates the area of the gas to be measured according to the area. The concentration of the gas can obtain higher detection accuracy.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

Claims (10)

1. A gas detection lidar based on a broad spectrum light source, comprising: the device comprises a wide-spectrum light source, a multi-channel filter, a pulse generation and power amplification module, a laser beam transceiving module, a wavelength division multiplexing de-multiplexing module, a multi-channel detection module, a data acquisition module and a data processing module;

the wide-spectrum light source is used for emitting wide-spectrum laser;

the multi-channel filter is used for filtering wide-spectrum laser emitted by the wide-spectrum light source into a plurality of laser signals with different frequencies, and the plurality of laser signals with different frequencies respectively correspond to different positions of an absorption curve of the gas to be detected; wherein, the full width at half maximum of the filtered curve corresponding to each frequency is smaller than a preset threshold value; the gas to be measured comprises one or more gases;

the pulse generation and power amplification module is used for chopping continuous light output by the wide-spectrum light source into pulse light and amplifying the power of the pulse light through the laser amplifier;

the laser beam transceiver module is used for emitting the amplified laser pulse to the gas to be detected and receiving a back scattering signal of the laser in the gas to be detected;

the wavelength division multiplexing module is used for demultiplexing laser backscattering signals of multiple frequencies to corresponding multiple optical fiber signal channels, and different optical fiber signal channels correspond to different signal frequencies;

the multichannel detection module comprises a plurality of detection channels and is used for detecting signals in the plurality of optical fiber signal channels demultiplexed by the wavelength division multiplexing module and outputting corresponding electric signals;

the data acquisition module is used for acquiring the electric signals output by the multi-channel detection module;

the data processing module is used for processing the echo signals of the multiple frequencies acquired by the data acquisition module, inverting the absorption spectra of the gas to be measured at different distances and calculating the gas concentrations at different distances.

2. A broad spectrum light source based gas detection lidar according to claim 1, wherein: the wide-spectrum light source is a wide-spectrum light source from ultraviolet to infrared bands.

3. A broad spectrum light source based gas detection lidar according to claim 1, wherein: the multichannel filter is a Fabry-Perot interferometer; the preset threshold is 100 MHz.

4. A broad spectrum light source based gas detection lidar according to claim 1, wherein: the laser beam transceiver module comprises a circulator and a telescope, the circulator is used for emitting the amplified laser pulse to the telescope, and the circulator is also used for transmitting a back scattering signal of the gas to be detected received and retrieved by the telescope to the wavelength division multiplexing module; the telescope is used for emitting laser beams to the gas to be measured and receiving back scattering signals of the gas to be measured.

5. A broad spectrum light source based gas detection lidar according to claim 1, wherein: the wavelength division multiplexing module is a WDM wavelength division multiplexer or a dispersion grating.

6. A broad spectrum light source based gas detection lidar according to claim 1, wherein: the wavelength division multiplexing module comprises a plurality of output ends, the multi-channel detection module comprises a plurality of corresponding detection channels, and each detection channel is used for detecting a signal output by the output end of the corresponding wavelength division multiplexing module.

7. A broad spectrum light source based gas detection lidar according to claim 6, wherein: the multichannel detection module comprises a multichannel photoelectric detector corresponding to the output waveband of the wide-spectrum light source.

8. The broad spectrum light source-based gas detection lidar of claim 6, wherein the multi-channel detection module comprises a plurality of photodetectors.

9. The broad spectrum light source based gas detection lidar of claim 1, wherein the data processing module comprises a nonlinear fitting unit and a gas concentration calculation unit;

the nonlinear fitting unit is used for obtaining absorption spectra at different distances according to the echo signals of the multiple frequencies acquired by the data acquisition module and performing nonlinear fitting on the absorption spectra to obtain a fitting curve;

and the gas concentration calculating unit is used for calculating the area of the fitting curve and calculating the concentration of the gas to be measured according to the area.

10. The broad spectrum light source based gas detection lidar of claim 1, wherein the non-linear fitting of the absorption spectrum comprises:

fitting the absorption spectrum by adopting a Lorentzian curve;

if the absorption spectrum contains an absorption peak, fitting a single-peak Lorentzian curve to the absorption spectrum;

and if a plurality of absorption peaks are contained in the absorption spectrum, fitting a multimodal Lorentzian curve to the absorption spectrum.

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