CN115015966A - Gas detection laser radar based on wide-spectrum light source - Google Patents
Gas detection laser radar based on wide-spectrum light source Download PDFInfo
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Abstract
The application provides a gas detection laser radar based on wide-spectrum light source relates to laser radar technical field, and this gas detection laser radar uses wide-spectrum laser instrument as the laser source, filters out the laser of a plurality of wavelengths through multichannel filter and is used for surveying the gas spectrum to adopt wavelength division multiplexer to carry out demultiplexing of a plurality of wavelengths and survey when a plurality of wavelengths when receiving, obtain the gaseous absorption line that awaits measuring of range resolution and spectral resolution. The invention uses the optical communication device to complete the remote sensing of the atmospheric gas components with wide spectrum, and has the following advantages: firstly, a plurality of single-frequency lasers are not needed, and the wide-spectrum light source can further improve the emergent power and reduce the system cost; secondly, synchronously detecting echo signals with multiple wavelengths to obtain an absorption spectrum of the gas to be detected and simultaneously have high space-time resolution; finally, the all-fiber system facilitates integration and miniaturization.
Description
Technical Field
The invention relates to the field of laser radars, in particular to a gas detection laser radar based on a wide-spectrum light source.
Background
The remote sensing of the atmospheric gas components has important significance for meteorological climate research, pollutant monitoring, atmospheric photochemical reaction research and the like.
The existing atmospheric gas component measurement mainly depends on in-situ measurement equipment and a laser radar, although the in-situ measurement technology can obtain various gas components with high precision, the gas component measurement distributed in a three-dimensional space cannot be obtained, the source of gas pollution and the propagation process of gas are difficult to position, and the laser radar is an effective way for realizing three-dimensional remote sensing of the atmospheric gas components.
The inventor finds that the gas detection laser radar mainly adopts a differential absorption laser radar, a path integral differential absorption laser radar and a high spectral resolution laser radar. The differential absorption laser radar selects laser with two wavelengths, one is located at the position where the absorption cross section of the gas to be detected is strong, and the other is located at the position where the absorption cross section of the gas to be detected is weak. The laser used for the differential absorption lidar needs to have a narrow line width and high wavelength stability, and different lasers are needed for different gases to be measured, so that the cost of the differential absorption lidar system is high. The wavelength scanning laser radar based on high spectral resolution can obtain various gas absorption spectra through scanning spectra, for example, the gas component detection laser radar based on the wavelength tunable laser provided by the invention patent with the patent application number of CN 201710651695.3. 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.
Disclosure of Invention
Technical problem to be solved
The invention aims to provide a gas detection laser radar based on a wide-spectrum light source, which is used for solving the problems that the conventional laser radar needs real-time laser wavelength locking and calibration in the scanning process, the system is complex, the scanning process consumes time and the time resolution is low.
(II) technical scheme
In order to achieve the purpose, the invention is realized by the following technical scheme: 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 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 detected 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 after the wavelength division multiplexing module demultiplexes 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 multiple frequencies acquired by the data acquisition module, inverting the absorption spectra of the gas to be detected at different distances and calculating the gas concentrations at different distances.
Further, the wide-spectrum light source is a wide-spectrum light source from ultraviolet to infrared bands.
Further, the multichannel filter is a Fabry-Perot interferometer; the preset threshold is 100 MHz.
Further, 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 backscatter signal of the gas to be detected received back by the telescope to the demultiplexing 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.
Further, the wavelength division multiplexing module is a WDM wavelength division multiplexer or a dispersion grating.
Furthermore, the wdm module includes a plurality of output ports, the multi-channel probe module includes a plurality of corresponding probe channels, and each probe channel is configured to probe a signal output by an output port of a corresponding wdm module.
Further, the multi-channel detection module comprises a multi-channel photodetector corresponding to a wide-spectrum light source output band.
Further, the multi-channel detection module comprises a plurality of photodetectors.
Furthermore, the photoelectric detector is a photomultiplier, a silicon detector, an indium gallium arsenic detector or a tellurium cadmium mercury detector.
Further, the data processing module performs inversion of the concentration of the gas to be detected by adopting a Lorentzian curve fitting algorithm, performs Lorentzian curve fitting on the multi-channel echo signal to obtain the area of an absorption curve of the gas to be detected, and calculates the concentration of the gas to be detected according to the area.
Further, the data processing module comprises a nonlinear fitting unit and a gas concentration calculating 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.
Further, fitting the absorption spectrum non-linearly comprises:
fitting the absorption spectrum by adopting a Lorentzian curve;
if the absorption spectrum comprises an absorption peak, fitting a unimodal Lorentz 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.
(III) advantageous effects
(1) According to the gas detection laser radar based on the wide-spectrum light source, the wide-spectrum light source is adopted, so that the defects that the stimulated Brillouin scattering effect is strong and the output power of a laser is limited due to the fact that the traditional laser radar is required to be provided with a narrow-line-width light source are overcome, and therefore the power and the signal-to-noise ratio of the laser radar can be remarkably improved through the wide-spectrum light source. The invention adopts the wide-spectrum light source to match with the multi-channel filtering module, does not need to be provided with a plurality of light sources, has low cost and wide coverage spectrum range, and can simultaneously detect a plurality of gases. In addition, compared with the narrow linewidth light source of the existing laser radar, the wide-spectrum light source adopted by the invention has low cost and great price advantage.
(2) The invention relates to a gas detection laser radar based on a wide-spectrum light source, which can realize the simultaneous detection of gas spectrums of various components by filtering a plurality of lasers with different frequencies through a multi-channel filter.
(3) The invention relates to a gas detection laser radar based on a wide-spectrum light source.A wavelength division multiplexer transmits atmospheric echo signals with multiple frequencies to a multi-channel detector for signal detection, so that the detection of a gas spectrum with high space-time resolution is completed.
(4) According to the gas detection laser radar based on the wide-spectrum light source, the data processing module adopts a Lorentz curve fitting algorithm to carry out inversion on the concentration of the gas to be detected, Lorentz curve fitting is carried out on multi-channel echo signals to obtain the area of an absorption curve of the gas to be detected, the concentration of the gas to be detected is calculated according to the area, and higher detection precision can be obtained.
Drawings
Fig. 1 is a schematic structural diagram of a gas detection laser radar based on a wide-spectrum light source according to an embodiment of the present invention;
FIG. 2 is a spectrum diagram of a wide-spectrum light source at a location according to an embodiment of the present invention;
FIG. 3 is a spectrum of a light source at a position after passing through a multi-channel filter according to an embodiment of the present invention;
FIG. 4 is an atmospheric gas absorption line at a location provided by an embodiment of the present invention;
FIG. 5 shows radar echo signals of different wavelengths according to an embodiment of the present invention;
fig. 6 is a transmittance curve of each channel of the demultiplexer according to the embodiment of the present invention;
FIG. 7 is a graph of measured gas absorption intensity of multi-wavelength detection after data processing at a location and a non-linearly fitted gas absorption spectrum according to an embodiment of the present invention;
FIG. 8 is a graph showing absorption spectra measured at different distances when the gas to be measured includes two gases according to an embodiment of the present invention.
Fig. 9 is a fitting curve obtained by fitting a bimodal lorentz curve to absorption spectra at different distances when the gas to be measured includes two gases according to the embodiment of the present invention.
Wherein, 1, a wide spectrum light source; 2. a multi-channel filter; 3. a pulse generation and power amplification module; 4. a power amplification module; 20. a laser beam transceiver module; 5. a circulator; 6. a telescope; 7. a de-wavelength division multiplexing module; 8. a multi-channel detection module; 9. a data acquisition module; 10. and a data processing module.
Detailed Description
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, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Examples
Referring to fig. 1, fig. 1 is a schematic structural diagram of a gas detection lidar based on a wide-spectrum light source according to an embodiment of the present invention, where the gas detection lidar includes: the device comprises a broad spectrum light source 1, a multi-channel filter 2, a pulse generation and power amplification module 3, a power amplification module 4, a laser beam transceiver module 20, a wavelength division multiplexing module 7, a multi-channel detection module 8, a data acquisition module 9 and a data processing module 10.
The output end of the wide-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 amplification module, and the output end of the power amplification module is connected with the input end of the laser beam transceiving module; the output end of the laser beam transceiving module is connected with the input end of the wavelength division multiplexing module, and the output end of the wavelength division multiplexing module is connected with the input end of the multi-channel detection module; the connections are all optical fiber connections. The multi-channel detection module, the data acquisition module and the data processing module are connected in sequence.
The wide-spectrum light source 1 is used for emitting wide-spectrum laser. The narrow linewidth light source required by the non-traditional laser radar has the narrower linewidth, the stronger the stimulated Brillouin scattering effect is, and therefore the output power of the laser is limited. The wide-spectrum light source is low in cost, wide in spectral line width and weak in stimulated Brillouin scattering effect, and therefore the power of the light source can be improved.
In one embodiment, the wide-spectrum light source 1 is a wide-spectrum light source in a range from ultraviolet to infrared, so that multiple gas absorption lines can be covered, and the gas detection capability of the laser radar is improved.
In one embodiment, the broad spectrum light source 1 is an ASE spontaneous emission light source or a white light source. The ASE spontaneous radiation light source has the advantages of low cost and wide coverage spectrum range.
The wide-spectrum light source selects laser with small loss in the 1-2 μm wave band in the optical fiber, preferably 1.5 μm wave band. The band is safe to human eyes and has low transmission loss.
The multi-channel filter 2 is used for filtering a wide-spectrum light source into a plurality of laser signals with different frequencies, and the plurality of different frequencies respectively correspond to different positions of an absorption curve of the gas to be measured; and 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.
Further, the multi-channel filtering
The device is a Fabry-Perot interferometer; the preset threshold is 100 MHz. Because the invention needs to measure a plurality of gases simultaneously through one gas absorption curve, the half-maximum width of the gas absorption curve to be measured corresponding to each filtered frequency is too large, so that two gases cannot be distinguished. The inventor of the present invention has found through research that when the threshold value is 100MHz, different gas components can be distinguished through the gas absorption curve to be measured.
A Fabry-perot interferometer (FPI) is a multi-beam interferometer composed of two parallel glass plates. Wherein the opposing inner surfaces of both glass sheets have a high reflectivity.
For a fabry-perot etalon, the significant variation in transmission with wavelength is due to the interference of multiple reflections between two reflective plates. The transmitted light has constructive interference when they are in phase, corresponding to a peak in etalon transmission; and when the transmitted light is reversed corresponds to a minimum value of transmittance. Whether multiple reflected lights are in phase with each other depends on the frequency of the incident light, the angle of refraction at which the light propagates within the etalon, the thickness of the etalon, and the refractive indices of the materials used.
Optical path difference between two adjacent reflected lights in Fabry-Perot etalon
The phase difference without taking into account the phase shift is
Wherein n is the refractive index in the standard inter-cavity; l is the cavity length of the etalon,
is the central wavelength of the incident light;
is the angle of incidence;
in addition, when the internal interface reflectivity is R, the transmission function T of the etalon e Is given by
When the optical path difference between two adjacent beams is an integral multiple of the wavelength, the transmittance function has a maximum value of 1. Reflectivity R of an etalon without absorption by the medium e Satisfy the requirement of
When in use
I.e. the transmission function has a minimum value when the optical path difference is half an odd multiple of the wavelength, which corresponds to a maximum value R of the reflectivity max
The wavelength separation between two adjacent transmission peaks in the transmission function is called the free spectral distance (FSR) of the etalon, which is given by:
wherein,
the free spectral spacing of the etalon is represented,
is the center wavelength of the nearest peak.
Because the invention needs to measure a plurality of gases on one absorption line at the same time, the invention has special requirements on the free spectrum spacing of the multi-channel filter, the free spectrum spacing needs to be less than 6.25GHz, the full width at half maximum of the transmittance curve needs to be less than 100MHz, and the full width at half maximum can not be used for detecting the gas absorption line.
The FPI can generate a transmittance curve with a free spectrum spacing of 6.25GHz and a full width at half maximum of less than 100MHz, further completes multi-channel filtering of a wide spectrum, and generates light beams with multiple frequencies for wide-spectrum gas detection.
Thus, the multi-channel filter is a fabry-perot interferometer; the preset threshold is 100 MHz.
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 pulse generating and power amplifying module comprises a pulse generator 3 and a power amplifier 4.
The pulse generator 3 is used for chopping the wide-spectrum light source into pulsed light. The pulse generator is an electro-optical modulator EOM, an acousto-optical modulator AOM and the like.
The power amplifier 4 is used for power amplification of the pulse light; the power amplifier is preferably a fiber laser amplifier, such as an erbium doped fiber amplifier EDFA or the like.
The laser beam transceiver module 20 is configured to emit the amplified laser pulse to the atmosphere and receive a backscatter signal of the laser in the atmosphere.
The wavelength division multiplexing module 7 is configured to demultiplex the laser backscatter signals of multiple frequencies into corresponding multiple optical fiber signal channels. Different fiber optic signal paths correspond to different signal frequencies.
Further, the wavelength division multiplexing module 7 is a WDM wavelength division multiplexer or a dispersion grating. Wdm (wavelength Division multiplexing), i.e. wavelength Division multiplexer.
The multi-channel detection module 8 comprises a plurality of detection channels, and is used for detecting echo signals in the plurality of optical fiber signal channels after demultiplexing and outputting corresponding electric signals; echo signals of different frequencies are obtained by different detection channels.
The input end of the demultiplexing module 7 is connected with the output end of the laser beam transceiving module 20, the output end of the demultiplexing module 7 comprises a plurality of optical fiber channels, and the plurality of optical fiber channels of the demultiplexing module 7 are respectively connected with the plurality of detection channels correspondingly.
In one embodiment, the demultiplexing module comprises a plurality of outputs, and the multi-channel probe module comprises a corresponding plurality of probe channels, each probe channel being configured to probe a signal output by a corresponding one of the outputs of the demultiplexing module.
The multi-channel detection module comprises a multi-channel photoelectric detector corresponding to the output waveband of the wide-spectrum light source. Therefore, multi-channel detection can be realized only by one multi-channel detector, the system structure is simplified, and the system cost and the volume are saved.
In another embodiment, the multi-channel detection module includes a plurality of photodetectors.
The photoelectric detector is a photomultiplier, a silicon detector, an indium-gallium-arsenic detector or a mercury-cadmium-telluride detector.
The data acquisition module 9 is used for acquiring the electric signals output by the multi-channel detection module 8.
The data processing module 10 is configured to process echo signals of multiple frequencies, invert absorption spectra of the gas to be measured at different distances, and calculate gas concentrations at different distances.
Furthermore, the data processing module adopts a Lorentz curve fitting algorithm to carry out inversion on the concentration of the gas to be detected, Lorentz curve fitting is carried out on the multi-channel echo signals to obtain the area of an absorption curve of the gas to be detected, and the concentration of the gas to be detected is calculated according to the area.
Further, the laser beam transceiver module 20 includes a circulator 5 and a telescope 6, the circulator 5 is configured to emit the amplified laser pulse to the telescope, and is further configured to transmit the atmosphere backscatter signal received by the telescope 6 to the demultiplexing module 7; the telescope 6 is used for emitting laser beams into the atmosphere and receiving atmosphere backscattering signals.
Based on all the above embodiments of the present invention, the following description will explain the specific working principle.
Referring to fig. 2, fig. 2 is a spectrum diagram of a wide-spectrum light source at a certain position according to an embodiment of the present invention.
As shown in fig. 2, which corresponds to point a in fig. 1, is located between the broad spectrum light source 1 and the multi-channel filter 2, and fig. 2 illustrates the spectrum of the broad spectrum light source emitted from the broad spectrum light source 1.
Referring to fig. 3, a spectrum diagram of a light source at a certain position after passing through a multi-channel filter is provided according to an embodiment of the present invention.
As shown in fig. 3, which corresponds to point b in fig. 1, and is located between the multi-channel filter 2 and the pulse generation module 3, fig. 3 illustrates a spectrum of a wide-spectrum light source filtered by the multi-channel filter, where, for example, a fabry-perot interferometer with a free spectrum spacing of 6.25GHz is used as the multi-channel filter, and λ 1, λ 2, λ 3, λ 4, λ 5, λ 6, and λ 7 are central wavelengths filtered by the respective channels.
Referring to fig. 4, fig. 4 is a view illustrating an atmospheric gas absorption line at a certain position according to an embodiment of the present invention.
As shown in fig. 4, which corresponds to point c in fig. 1, is located in the atmosphere behind the laser beam transceiver module 20, and fig. 4 illustrates absorption lines of the gas to be measured.
Referring to fig. 5, fig. 5 shows radar echo signals with different wavelengths according to an embodiment of the present invention.
As shown in fig. 5, which corresponds to point d in fig. 1, between the circulator 5 and the demultiplexer 7, the multichannel filter 2 filters out 7 channels, here showing echo signals of two channels with center wavelengths λ 1 and λ 4.
Referring to fig. 6, fig. 6 is a transmittance curve of each channel of the demultiplexer according to the embodiment of the present invention.
As shown in fig. 6, it corresponds to point e in fig. 1, and is located in the demultiplexing module 7, the central wavelength and the channel interval of each channel of the demultiplexing module correspond to the multichannel filter, the central wavelength positions are λ 1, λ 2, λ 3, λ 4, λ 5, λ 6 and λ 7, the demultiplexing module 10 demultiplexes the echo signal of each wavelength into multiple optical fibers, the demultiplexed multichannel echo signal is received by the multichannel detection module 8, and the electrical signal output by the detection module is transmitted to the data acquisition module 9 for acquisition.
Referring to fig. 7, fig. 7 shows the measured gas absorption intensity of multi-wavelength detection after data processing at a certain position and a non-linearly fitted gas absorption spectrum according to an embodiment of the present invention.
As shown in fig. 7, which corresponds to point f in fig. 1, the data processing module 10 is located in the data processing module 10, and after obtaining the echo signals of each channel, the data processing module 10 processes the obtained absorption coefficients of multiple wavelengths at each distance, where the absorption coefficients of 7 wavelengths at one distance are shown as circles in fig. 7. Further, the obtained multi-wavelength absorption coefficient is subjected to nonlinear fitting to obtain a gas absorption spectrum line to be detected at the distance, and finally the gas absorption characteristic to be detected with spectral resolution, time resolution and spatial resolution is obtained.
Further, the data processing module performs inversion of the concentration of the gas to be detected by adopting a Lorentzian curve fitting algorithm, performs Lorentzian curve fitting on the multi-channel echo signal to obtain the area of an absorption curve of the gas to be detected, and calculates the concentration of the gas to be detected according to the area.
Specifically, the data processing module comprises a nonlinear fitting unit and a gas concentration calculating 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.
Specifically, since the concentration of the gas to be measured is determined by the partial pressure P, the partial pressure satisfies the following equation:
wherein A is the Lorentzian linear area of the absorption coefficient, P is the partial pressure of the gas to be detected, T is the temperature of the gas to be detected, T0 = 273.15K, P0 = 100 kPa, n L The spectral line intensity of the gas to be measured at T0 and P0. The area A can be obtained by Lorentzian line type fitting of the measured absorption coefficient, and the partial pressure P can be further calculated, so that the concentration of the gas to be measured can be obtained.
In the present invention, Lorentzian curve fitting is preferred as the non-linear fitting.
Further, fitting the absorption spectrum non-linearly 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.
The multiple absorption peaks correspond to one or more gases in the gas to be detected; and if the absorption spectrum contains N gas absorption peaks, performing N-peak fitting on the absorption spectrum to respectively obtain a fitting curve of the gas corresponding to each absorption peak. And calculating 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 lorentz curve to absorption spectra at different distances when the gas to be measured contains only one gas.
Fig. 8 shows absorption spectra measured at different distances when the gas to be measured includes two gases.
Fig. 9 is a fitting curve obtained by fitting a bimodal lorentz curve to absorption spectra at different distances when the gas to be measured contains two gases. When the gas concentration is calculated, the concentrations of the two gases can be obtained by respectively calculating the two fitting curves.
In summary, the gas detection laser radar based on the wide-spectrum light source provided by the invention overcomes the defects that the traditional laser radar has strong stimulated brillouin scattering effect due to the requirement of a narrow-line-width light source, and further limits the output power of a laser, and therefore, the wide-spectrum light source can obviously improve the power and the signal-to-noise ratio of the laser radar. The invention adopts the wide-spectrum light source to match with the multi-channel filtering module, does not need to be provided with a plurality of light sources, has low cost and wide coverage spectrum range, and can simultaneously detect a plurality of gases.
The invention filters out a plurality of lasers with different frequencies by adopting the multi-channel filter for detection, and can realize the gas spectrum simultaneous detection of a plurality of components because a plurality of different frequency components are respectively positioned at different positions of the absorption line to be detected.
The wavelength division multiplexer transmits the atmospheric echo signals with a plurality of frequencies to the multichannel detector for signal detection, thereby completing the detection of the gas spectrum with high space-time resolution.
Compared with the narrow linewidth light source of the existing laser radar, the wide-spectrum light source adopted by the invention has low cost and great price advantage.
The optical fiber communication device used by the invention is mature, such as a multi-channel filter and a wavelength division multiplexer, and can complete the detection of the gas absorption spectrum with wide spectrum.
The data processing module adopts a Lorentz curve fitting algorithm to carry out inversion on the concentration of the gas to be detected, Lorentz curve fitting is carried out on the multi-channel echo signal to obtain the area of an absorption curve of the gas to be detected, the concentration of the gas to be detected is calculated according to the area, and higher detection precision can be obtained.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises 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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