Absorption spectrum parameter solving method and device for extracting same-phase point of modulation spectrum

Abstract

The invention discloses an absorption spectrum parameter solving method and device for extracting a same-phase point of a modulation spectrum, and the method comprises the steps: S1, enabling a laser generation module to drive a laser to emit modulation laser through employing a high-frequency sinusoidal signal and a low-frequency sinusoidal signal which are superposed as a modulation signal generated by laser, enabling the laser to pass through a to-be-detected gas area to carry absorption spectrum information; s2, a laser signal detection module and a high-speed data acquisition module are used for detecting and acquiring laser absorption spectrum signals; and S3, performing in-phase extraction and uploading on the acquired spectral signals by an in-phase extraction and uploading module, sequentially substituting wavelength change information and light intensity information of each grouped phase point into the direct absorption linear model for fitting iteration, and solving parameters of the gas to be detected. By adopting the technical scheme provided by the invention, the anti-noise capability of the modulation method is reserved, and meanwhile, the direct absorption spectrum parameters are quickly solved.

Description

Technical Field

[0001] The invention belongs to the technical field of laser absorption spectrum, and in particular relates to a method and device for solving absorption spectrum parameters of in-phase points of a modulation spectrum. Background Art

[0002] Tunable Diode Laser Absorption Spectroscopy (TDLAS) is a high-resolution infrared laser absorption spectroscopy technique that emerged in the mid-1960s with the development of tunable lasers. TDLAS has unique advantages such as non-contact non-destructive testing, high sensitivity, real-time dynamics, and simultaneous measurement of multiple components and parameters. Since its birth, it has been favored by combustion researchers, and its application in the field of combustion diagnosis has become more extensive and diverse in the past decade.

[0003] At present, the main methods of TDLAS are direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS). DAS applies a linear scanning current to accurately record the change of laser wavelength while collecting gas laser absorption signals, and then directly fits the ratio of transmitted light intensity to incident light intensity to obtain the gas absorption rate linear function, and then obtains the relevant parameters of the absorption spectrum. The WMS method generally controls the laser by superimposing a sinusoidal signal on the sawtooth wave, and then demodulates the collected signal to obtain some parameters of the laser absorption line. Due to the modulation and demodulation process, the signal-to-noise ratio of the signal measured by WMS is higher than that of the DAS method, but at the same time, the absorption spectrum cannot be fully restored due to the filtering and demodulation process.

[0004] In recent years, methods for recovering absorption spectrum parameters based on wavelength-modulated absorption spectra have also been studied. Compared with the DAS method, the WMS method has no way to directly obtain the baseline of the DAS. Therefore, how to recover the absorption obtained by the WMS signal is the first problem that the WMS method faces in recovering the absorption spectrum parameters. Since the WMS signal can generate multiple harmonics, Masataka Nakazawa et al. published a paper entitled "Phase-sensitive detection on Lorentzian line shape and its application to frequency stabilization of lasers" in the Journal of Applied Physics, Vol. 59, No. 7, p. 2297 in 1986. The paper described the phase-sensitive detection of the Lorentzian line shape using the Fourier expansion method and the residual method. The relationship between the modulation broadening and the modulus can be used to obtain the half-height width of the Lorentzian profile. This method relies on an accurate phase detector and is very sensitive to noise. Ove Axner et al. published a paper titled "Theoretical description based on Fourier analysis of wavelength-modulation spectrometry in terms of analytical and background signals" on page 5803 of Volume 38 of Applied Optics in 1999. The paper gave a theoretical description of wavelength-modulation absorption spectroscopy based on Fourier analysis, proposed a form that is not limited to low modulation amplitudes, and proposed a method for removing background signal interference in 2f harmonic signals.Kevin Duffin et al. published a paper titled "Tunable Diode-Laser Spectroscopy With Wavelength Modulation: A Calibration-Free Approach to the Recovery of Absolute Gas Absorption Line Shapes" on page 367 of Volume 150 of the Journal of Lightwave Technology in 2007. The paper proposed a method for recovering absorption spectrum line shapes based on the residual modulation amplitude signal of the modulation signal. This method utilizes the phase delay condition of the laser that changes with the modulation speed and depth to optimize the relevant approximate conditions, and is therefore also limited by specific modulation conditions. In addition, in order to avoid interference from background signals, differential detection of signals has also been studied. In 2010, Thilo Kraetschme et al. published a paper titled "Background-free absorption spectroscopy using delayed balanced detection" in Applied Physics B, Vol. 98, p. 249. They added a fiber delay to the detection light path to create a phase difference between the reference light and the detection signal, thereby forming differential detection and achieving automatic calibration of the background signal. However, this method requires accurate control of the phase difference of the optical fiber, and has high requirements on the working environment and quality of the optical fiber. In 2019, Vladimir Liger et al. published a paper titled "Advanced Fiber-Coupled Diode Laser Sensor for Calibration-Free 1f-WMS Determination of an Absorption Line Intensity" on page 249 of Volume 98 of Sensors. They designed a method to measure the absorption spectrum signal by performing differential operations on the detection signal using a differential detection circuit, which effectively improved the accuracy of the measurement results under strong background interference.Chen Ke et al. published an article titled "An auto-correction laser photoacoustic spectrometerbased on 2f / 1f wavelength modulation spectroscopy" on page 1524 of Volume 145 of "Analyst" in 2020. The article introduces a laser photoacoustic self-correction spectrometer based on 2f / 1f wavelength modulation spectroscopy for the detection of trace gases to eliminate the concentration measurement error caused by optical power changes. The above methods are to introduce parameters such as optical fiber devices or harmonic signals under special modulation waveforms into the detection optical path under certain conditions. These methods can solve the problem of obtaining absolute absorption signals based on WMS signals to a certain extent, but with the introduction of additional systems or the limitation of special modulation conditions, the system becomes complicated and is also limited in specific applications.

[0005] There are also many studies on the method of linear fitting directly for the harmonic signal of WMS signal in combination with database. In 2009, Hong Duan et al. published a paper titled "Harmonic wavelet analysis of modulated tunable diode laser absorption spectroscopy signals" on page 401 of Volume 48 of Applied Optics. They conducted a wavelet analysis on the tunable semiconductor laser absorption spectroscopy signal and found that the wavelet analysis-based method can simultaneously extract 1f, 2f and high-order harmonics from direct absorption data, which can be used to realize signal analysis and extraction. Ronald K Hanson et al. published a paper titled "Calibration-free wavelength-modulation spectroscopy for measurements of gas temperature and concentration in harsh environments" on page 5546 of volume 48 of Applied Optics in 2009. The paper introduced a calibration-free method for 2f / 1f signals. The method used the first harmonic signal to correct the second harmonic signal, eliminated the influence of laser intensity fluctuation, photoelectric gain and other factors, and derived the absolute gas concentration expression. Later, Sun.Kai et al. published an article titled "Analysis of calibration-free wavelength-scanned wavelength modulation spectroscopy for practical gas sensing using tunable diode lasers" on page 125203 of volume 24 of Measurement Science & Technology in 2013. The paper proposed a method for analyzing and extracting harmonic information based on the Fourier model.Christopher S. Goldenstein et al. published the article "Fitting of calibration-free scanned-wavelength modulation spectroscopy spectra for determination of gas properties and absorption line shapes" in Applied Optics, Vol. 53, p. 356 in 2014, introducing the fitting of nf / 1f harmonics to obtain relevant absorption spectrum information. Zhechao Qu et al. published the article "Calibration-free scanned wavelength modulation spectroscopy-application to H2O and temperature sensing in flames" in Optics Express, Vol. 23, p. 164929 in 2015, proposing a calibration-free scanning wavelength modulation spectroscopy scheme that requires minimal laser characteristics. In a single fit of a set of 2f / 1f-WMS line shapes obtained in one laser scan, the concentration and temperature of the substance are obtained simultaneously. In the paper "Absorption Spectrum Measurement Method Based on Nonlinear Synchronous Fitting of Light Intensity and Absorption Rate" published in Volume 67, No. 057801 of "Acta Physica Sinica" in 2018, Li Ning et al. proposed to use nonlinear fitting method to couple laser intensity and absorption spectrum in laser absorption spectrum measurement, establish the relationship between nonlinear change of laser intensity and multi-line absorption fitting function, solve the problem of not being able to obtain spectral baseline under special environment, and realize the separation and diagnosis of spectral signals after wavelength division multiplexing process. The feasibility of this method was verified by simulation, and the influence of factors such as laser characteristics and characteristic spectral line position on the fitting results was analyzed and calculated. In 2018, Du Yanjun et al. published "High-accuracy sinewave-scanned direct absorption spectroscopy" in Optics Express, Vol. 26, p. 29550. They introduced an absorption spectrum measurement method based on direct absorption method and wavelength modulation method. They used low-frequency sinusoidal signals to drive the laser modulation and realized the modulation, demodulation and calculation of the absorption spectrum parameters. This method is a direct absorption method in the form of sinusoidal scanning, which is suitable for accurate absorption spectrum line type calibration in experiments.The above fitting method inherits the idea of ​​fitting the absorption spectrum in DAS. However, in the fitting process based on the harmonic signal, due to the coupling relationship of the laser absorption spectrum, it is necessary to perform simulation fitting for the entire filter demodulation system when establishing the simulation fitting of the absorption spectrum, which not only introduces a lot of uncertainties, but also makes the whole process more complicated.

[0006] Based on the above problems, some researchers began to abandon the direct use of WMS harmonic signals and began to extract new characteristic information from WMS harmonic signals for absorption spectrum parameter solution. Wei Wei et al. published a paper titled "Eliminating the effect of phase shift between injection current and amplitude modulation in DFB-LD WMS for high-precision measurement" on page 3526 of Volume 55 of Applied Optics in 2016. The paper discussed the phase shift between injection current and amplitude modulation caused by the characteristics of semiconductor lasers. The phase shift has no obvious regularity, but has a significant impact on the measurement results. In particular, a new method is proposed for high-precision measurement to suppress the influence of this phase shift. The phase shift fluctuation between injection current and amplitude modulation is suppressed to 0.72 degrees to 0.07 degrees, thereby improving the measurement accuracy. Abhishek Upadhyay et al. published a paper titled "A New RAM Normalized 1f-WMS Technique for the Measurement of Gas Parameters in Harsh Environments and a Comparison With 2f / 1f" on page 99 of Volume 1 of the IEEE Photonics Journal in 2018. The paper introduces a calibration-free first harmonic (1f) wavelength modulation spectroscopy technique for measuring gas component parameters. In this technique, the total amplitude of the 1f-WMS signal is normalized by a component of the 1f residual amplitude modulation signal. This method retains the advantages of the traditional nf / 1f method, which can accurately restore gas parameters without being affected by background signals, and does not require background normalization at high pressure or high modulation coefficients.In 2019, Jianxin Liu et al. published a paper titled "A novel methodology to directly predetermine the relative wavelength response of DFB laser in wavelength modulation spectroscopy" on page 1249 of Optics Express, volume 27. This paper introduces a method for inferring the relative wavelength response of DFB laser in wavelength modulation spectroscopy (WMS) based on the current linear scanning wavelength response and the current modulation wavelength response for more accurate fitting and effective improvement. In 2020, Zhou Peili et al. published a paper titled "Reproduction method based on even harmonic absorptivity function" on page 293 of Laser & Infrared, volume 50. This paper proposes a method for recovering the absorption line shape using the even harmonic components of the wavelength modulated signal. This method constructs the relationship between the absorption line shape and the higher harmonics of the modulation signal based on the Taylor expansion form of the absorption line shape, and is therefore limited by the conditions of the Taylor expansion, that is, the approximation under the condition of small modulation. During the modulation process, there is a strong nonlinear relationship between the wavelength and intensity of the laser, which also affects the realization of the measurement. In response to this problem, relevant research work has also been widely carried out. Yun Pan et al. published an article titled "Improvement of Concentration Inversion Model Based on Second Harmonic Valley Spacing in Wavelength Modulation Spectroscopy" on page 164929 of Volume 23 of IEEE Access in 2020. The article introduced the change of the second harmonic peak due to the change of modulation depth, and proposed a method to calibrate the modulation depth and use it as a parameter of the concentration inversion model. The method verifies the effectiveness of using valley spacing for modulation depth calibration and the accuracy of the improved model. Although the above method can establish a mapping relationship between harmonic information and gas parameters and solve the absorption spectrum parameters through these harmonic characteristic points, it is necessary to calibrate the test process in advance, which makes the whole process complicated.

[0007] In summary, in the process of using the WMS method to recover the absorption spectrum parameters, while using the high signal-to-noise ratio brought by the harmonic signal generated by the WMS modulation signal, due to the problem of coupling the luminous intensity and wavelength of the current-modulated semiconductor laser, it is difficult to obtain the absolute absorbance of the modulated signal and calibrate the laser characteristics. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a method and device for solving the absorption spectrum parameters by extracting the in-phase points of the modulation spectrum, which uses the light intensity data of the in-phase points of the modulation signal, retains the anti-noise ability of the modulation method, and realizes the rapid solution of the absorption spectrum parameters. It has broad application prospects in the field of laser absorption spectrum parameter measurement.

[0009] To achieve the above object, the present invention adopts the following technical solution:

[0010] A method for solving absorption spectrum parameters of points with the same phase of a modulation spectrum, comprising:

[0011] Step S1, the laser generating module uses a high-frequency sinusoidal signal superimposed with a low-frequency sinusoidal signal as a modulation signal for laser generation to drive the laser to emit a modulated laser and make the laser pass through the gas region to be measured to carry absorption spectrum information;

[0012] Step S2, using a laser signal detection module and a high-speed data acquisition module to detect and acquire laser absorption spectrum signals;

[0013] Step S3, the in-phase extraction and upload module extracts and uploads the collected spectral signal in-phase, and sequentially substitutes the wavelength change information and modulation information of each phase point after grouping into the direct absorption line model for fitting iteration to solve the gas parameters to be measured.

[0014] Preferably, in step S1, a laser generating module is provided to control the laser to generate wavelength modulated laser at a set frequency.

[0015] Preferably, in step S3, the in-phase extraction and uploading module extracts and uploads the in-phase of the collected spectral signal according to the light intensity data of the in-phase point of the sinusoidal signal.

[0016] The present invention also provides a device for solving absorption spectrum parameters for extracting the same-phase points of the modulation spectrum, comprising:

[0017] The first processing module is used for the laser generating module to use the high-frequency sinusoidal signal and the low-frequency sinusoidal signal superimposed as the modulation signal for laser generation to drive the laser to emit modulated laser light, and make the laser light pass through the gas area to be measured to carry the absorption spectrum information;

[0018] A second processing module is used to detect and collect laser absorption spectrum signals using a laser signal detection module and a high-speed data acquisition module;

[0019] The third processing module is used for the in-phase extraction and uploading module to extract and upload the collected spectral signal in-phase, and substitute the wavelength change information and modulation information of each phase point after grouping into the direct absorption line model in turn for fitting iteration to solve the gas parameters to be measured.

[0020] Preferably, the first processing module controls the laser to generate wavelength modulated laser at a set frequency by setting a laser generating module.

[0021] Preferably, the third processing module enables the in-phase extraction and uploading module to extract and upload the in-phase of the collected spectral signal according to the light intensity data of the in-phase point of the sinusoidal signal.

[0022] The present invention solves the above-mentioned problem of wavelength modulation method in solving absorption spectrum parameters. First, the laser is controlled to generate wavelength modulated laser according to the set frequency; secondly, synchronous collection is performed according to the set sampling rate and laser control module excitation; finally, a time-domain in-phase extraction strategy is designed according to the modulation frequency and sampling rate, and the collected data is grouped and substituted into the absorption spectrum line function for fitting to obtain the absorption function for solution. The present invention makes full use of high-speed data acquisition technology to quickly obtain data points that can be used for absorption spectrum data fitting, and at the same time, the fitting effect of multiple sets of data obtained quickly is used to improve the accuracy of the fitting results. The present invention is simple and effective, and can provide a new means for temperature sensing and concentration sensing based on laser absorption spectrum parameter measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0024] Figure 1 A flow chart of a method for solving absorption spectrum parameters of in-phase points of a modulation spectrum extracted according to an embodiment of the present invention;

[0025] Figure 2 Schematic diagram of the principle of the method for extracting absorption spectrum parameters of the same-phase points of the modulation spectrum;

[0026] Figure 3 Schematic diagram of current signal for modulating laser; wherein (a) is the laser wavelength signal sequence, and (b) is the absorption signal sequence;

[0027] Figure 4 Schematic diagram of the convergence process of parameter solution iteration; wherein (a) is the absorbance obtained by processing the collected laser absorption spectrum data; (b) is the iterative convergence curve of the absorption spectrum parameter X; (c) is the iterative convergence curve of the absorption spectrum parameter γ; DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Embodiment 1:

[0031] like Figure 1 , 2 As shown, the present invention provides a method for solving absorption spectrum parameters for extracting the same-phase points of the modulation spectrum, which is used to solve the absorption spectrum parameters required for laser absorption spectrum temperature and concentration sensing, including the following steps:

[0032] Step S1, the laser generating module uses a high-frequency sinusoidal signal superimposed with a low-frequency sinusoidal signal as a modulation signal for laser generation to drive the laser to emit a modulated laser, and the laser passes through the gas region to be measured to carry absorption spectrum information;

[0033] Step S2, using a laser signal detection module and a high-speed data acquisition module to detect and acquire laser absorption spectrum signals;

[0034] Step S3, the in-phase extraction and upload module extracts and uploads the collected spectral signal in-phase, and sequentially substitutes the wavelength change information and modulation information of each phase point after grouping into the direct absorption line model for fitting iteration to solve the gas parameters to be measured.

[0035] As an implementation method of an embodiment of the present invention, the laser generating module uses a high-frequency sinusoidal signal and a low-frequency sinusoidal signal superimposed as a modulation signal for laser generation to drive the laser to emit laser light. After the laser passes through the gas area to be measured, a laser absorption spectrum signal is formed. The laser signal detection module and the high-speed data acquisition module are used to detect and collect the laser absorption spectrum signal. The low-frequency modulation signal frequency f L With high frequency signal modulation frequency f H , and the sampling rate fs , it is necessary to satisfy the integer multiple relationship of the following equations (1), (2) and (3):

[0036]

[0037] Where R is the number of points of a single frame signal, M is the total number of sampling points, and N is the total number of groups of signals that can be obtained within the sampling period; if F is not an integer, the number of points of M can be expanded upward to a divisible number of points by interpolation; if N is not an integer, it is rounded down to an integer;

[0038] The laser generating module uses a low-frequency signal generator 101 and a high-frequency signal generator 102 to generate low-frequency and high-frequency driving currents to a signal superimposed device 103, and then outputs the currents to a laser controller 104 to control a laser 105 to emit a modulated laser. The modulated sinusoidal signal I0(t) is in the following form:

[0039]

[0040] Among them, I L with I H are the low-frequency modulation and high-frequency modulation signal strengths, respectively. and is the initial phase of the modulation signal. The wavelength change v0 of the laser signal generated thereby is in the form of:

[0041]

[0042] Among them, V L With V H is the wavelength modulation depth, and is the initial phase of wavelength modulation; the laser intensity signal generated thereby can be expressed as:

[0043]

[0044] Among them, a L1 with a L2 are the signal strengths of low frequency modulation one-fold and two-fold, respectively, a H1 with a H2 They are the signal strengths of high-frequency modulation one-fold and two-fold, and are the corresponding modulation phases respectively; the modulated laser is divided into three beams by the optical fiber beam splitter 106, and passes through the gas area 107 to be measured respectively. Assuming that the gas absorption rate is α(v), the corresponding laser transmittance is τ(v), then the detection signal I t It can be expressed as:

[0045] A t(t)=A0(t)τ(v(t))=A0(t)exp(α(v0(t))) (7)

[0046] The laser intensity reference signal detected by the second photodetector 111 through the optical fiber 108 can be expressed as:

[0047]

[0048] After being detected by the third photodetector 112 through the interferometer 109 as a laser wavelength change signal, the sampled discrete v0 can be expressed as v0(k), where k = 1, 2, 3...M,

[0049]

[0050] The absorption intensity signal detected by the first photodetector 110 can be expressed as A t (k):

[0051] A t (k)=A0(k)exp(α(v0(k))) (10)

[0052] After the spectral signal is detected by the laser signal detection module, it is collected by the high-speed data acquisition module 113. After the high-speed data acquisition module 113 collects the signals of the photoelectric detectors 110 and 111, the reference signal sequence A0(k) and the absorption signal sequence A0(k) can be directly obtained. t (k) If Figure 3 As shown in (b), the high-speed data acquisition module 113 collects the signal of the photodetector 112 and processes the interference peak to obtain the wavelength signal sequence v0(k), as shown in FIG. Figure 3 (a) as shown; the in-phase extraction and uploading module 114 extracts the in-phase point information of the collected spectral signal and uploads it to the computer 115,

[0053] According to the information of the modulation waveform, it is converted into the following matrix according to the following rules:

[0054]

[0055] As an implementation method of the embodiment of the present invention, in step S3, the wavelength change information and modulation information of each phase point after grouping are sequentially substituted into the direct absorption line model for fitting iteration, and the gas parameters to be measured are solved specifically as follows:

[0056] According to the relationship of absorption line type, we can get:

[0057]

[0058] α(V wave(i,j))=In(P(i,j)) (13)

[0059] Set up a sequence of fit points around the absorption line to be measured:

[0060] S v =(v0-nΔv,v0-nΔv+Δv,…,v0,…v0+nΔv-Δv,v0+nΔv) (14)

[0061] V wave The value in S v The nearest interpolation matching is performed in v The i-th fitting point in Corresponding absorption rate It can be obtained by averaging the corresponding points in the P matrix;

[0062] The obtained line type parameter expression can be expressed as:

[0063]

[0064] Where X is the area of ​​the absorption spectrum, φ(v) is the absorption line type of the gas, and the absorption rate obtained by processing the collected laser absorption spectrum data is as follows: Figure 4 As shown in (a), it can be expressed using the Voigt line type as follows:

[0065]

[0066] Among them, γ is the half width of the absorption line type, v0 is the center of the selected absorption line type, c l With c g are the proportions of Lorentzian linetype and Gaussian linetype respectively;

[0067] Set the iteration starting point:

[0068]

[0069] S v With S p Substitute the linear function for fitting and set D i-1 As the starting point of the i-th fit, obtain the parameter set representing α(v):

[0070]

[0071] Further determine whether to terminate the fitting based on the following criteria and output the results:

[0072] ε0>ε=p1σ(X)+p2σ(γ)+p3σ(c l )+p4σ(c g ) (19)

[0073] Among them, ε0 is the error threshold set, σ(X), σ(γ), σ(c l ),σ(c g ) are X i-o , X i-o+1 ,…X i-1 , X i The standard deviation of i-o , γ i-o+1 ,…γ i-1 , γ i The standard deviation of The standard deviation of The standard deviation of p1, p2, p3, and p4 are weights set according to the accuracy requirements of the solution parameters. When the calculated weighted error ε is less than the set value, the iteration is terminated and the linear parameter D is output. i .

[0074] The steps for performing an example are as follows:

[0075] Step 1: The low frequency signal generator 101 and the high frequency signal generator 102 generate a modulation signal. L =50mA and I H =50mA, f L =100Hz and f H =100kHz, and Set the laser temperature so that the central wave number of the laser scan is 7185 cm -1 , then set f s =100MHz, so n=1, M=1000, let R=10 6 , N = 1000R = 10 6 .

[0076] Step 2, the low-frequency signal generator 101 and the high-frequency signal generator 102 generate low-frequency and high-frequency control currents to the signal superimposer 103 and then output to the laser controller 104 to control the laser 105 to emit a modulated laser, which is divided into three beams by the optical fiber beam splitter 106, respectively passing through the gas area 107 to be measured, the component is a water vapor gas pool with a molar concentration of 0.01, detected as an absorption intensity signal by the first photodetector 110, detected as a laser intensity reference signal by the second photodetector 111 through the optical fiber 108, and detected as a laser wavelength interference signal by the third photodetector 112 through the interferometer 109. The three-way signal is collected by the high-speed data acquisition module 113, and the phase extraction and upload module 114 controls the laser controller 104 to control the laser to emit light at time t1, and controls the high-speed data acquisition module 113 to perform data acquisition at time t2;

[0077] Step 3: Collect the reference signal sequence A0 and the absorption signal sequence A t The wavelength signal sequence v0 obtained by analyzing the laser wavelength interference signal is converted into a 1000×1000 square matrix, and the matrix absorptivity matrix P and wavelength variation matrix V used for iterative calculation are solved; ε0=10 -5 , p1=1, p2=1, p3=1, p4=1, set the iteration starting point to: Where s, r are P(i, 1), the position index of half the maximum value is s, X0 = γ0P max1 , At the same time, the variance calculation step size o=10 is set, and ε is calculated until ε<ε0. The iteration is terminated and the parameters to be calculated are output. The iterative convergence of X and γ is obtained as follows: Figure 4 (b) and Figure 4 as shown in (c).

[0078] Embodiment 2:

[0079] The embodiment of the present invention further provides a device for solving absorption spectrum parameters for extracting in-phase points of a modulation spectrum, comprising:

[0080] The first processing module is used for the laser generating module to use the high-frequency sinusoidal signal and the low-frequency sinusoidal signal superimposed as the modulation signal for laser generation to drive the laser to emit modulated laser light, and make the laser light pass through the gas area to be measured to carry the absorption spectrum information;

[0081] A second processing module is used to detect and collect laser absorption spectrum signals using a laser signal detection module and a high-speed data acquisition module;

[0082] The third processing module is used for the in-phase extraction and uploading module to extract and upload the collected spectral signal in-phase, and substitute the wavelength change information and modulation information of each phase point after grouping into the direct absorption line model in turn for fitting iteration to solve the gas parameters to be measured.

[0083] As an implementation mode of the embodiment of the present invention, the first processing module controls the laser to generate wavelength modulated laser according to a set frequency by setting a laser generating module.

[0084] As an implementation of the embodiment of the present invention, the third processing module enables the in-phase extraction and uploading module to extract and upload the in-phase of the collected spectral signal according to the light intensity data of the in-phase point of the sinusoidal signal.

[0085] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for solving absorption spectrum parameters of the same-phase points of the modulation spectrum, characterized in that: include: Step S1, the laser generating module uses a high-frequency sinusoidal signal superimposed with a low-frequency sinusoidal signal as a modulation signal for laser generation to drive the laser to emit a modulated laser, and the laser passes through the gas region to be measured to carry absorption spectrum information; Step S2, using a laser signal detection module and a high-speed data acquisition module to detect and collect laser absorption spectrum signals; Step S3, the in-phase extraction and upload module extracts and uploads the collected spectral signal in-phase, and sequentially substitutes the wavelength change information and modulation information of each phase point after grouping into the direct absorption line model for fitting iteration to solve the gas parameters to be measured.

2. The method for solving the absorption spectrum parameters of the in-phase points of the modulation spectrum as claimed in claim 1, characterized in that: In step S1, a laser generating module is set to control the laser to generate wavelength modulated laser according to a set frequency.

3. The method for solving the absorption spectrum parameters of the in-phase points of the modulation spectrum as claimed in claim 2, characterized in that: In step S3, the in-phase extraction and uploading module extracts and uploads the in-phase of the collected spectral signal according to the light intensity data of the in-phase point of the sinusoidal signal.

4. A device for solving absorption spectrum parameters for extracting the same-phase points of a modulation spectrum, characterized in that: include: The first processing module is used for the laser generating module to use the high-frequency sinusoidal signal and the low-frequency sinusoidal signal superimposed as the modulation signal for laser generation to drive the laser to emit modulated laser light, and make the laser light pass through the gas area to be measured to carry the absorption spectrum information; A second processing module is used to detect and collect laser absorption spectrum signals using a laser signal detection module and a high-speed data acquisition module; The third processing module is used for the in-phase extraction and uploading module to extract and upload the collected spectral signal in-phase, and substitute the wavelength change information and modulation information of each phase point after grouping into the direct absorption line model in turn for fitting iteration to solve the gas parameters to be measured.

5. The device for solving absorption spectrum parameters for extracting the in-phase points of the modulation spectrum according to claim 4, characterized in that: The first processing module controls the laser to generate wavelength modulated laser according to a set frequency by setting the laser generating module.

6. The device for solving absorption spectrum parameters for extracting the in-phase points of the modulation spectrum according to claim 5, characterized in that: The third processing module enables the in-phase extraction and uploading module to extract and upload the in-phase of the collected spectral signal according to the light intensity data of the in-phase point of the sinusoidal signal.

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