Anti-interference broadband cavity enhanced absorption spectroscopy inversion method

Abstract

The present application relates to the technical field of gas concentration calculation, in particular to an anti-interference broadband cavity enhanced absorption spectrum inversion method. On the basis of the traditional cavity enhanced absorption spectrum algorithm, a pseudo-absorption function is constructed to represent the non-gas absorption structure caused by lamp spectrum change in the gas concentration inversion process, so as to separate the interference caused by lamp spectrum change from the gas absorption structure, effectively avoid the influence of lamp spectrum change on the gas concentration inversion result, overcome the dependence of the traditional cavity enhanced algorithm on the absolute stability of the light source, and realize the accurate quantification of the gas concentration. The method can effectively improve the robustness and environmental adaptability of the broadband cavity enhanced absorption spectrum system.

Description

Technical Field

[0001] The present invention relates to the technical field of gas concentration calculation, in particular to an anti-interference broadband cavity-enhanced absorption spectrum inversion method. Background Art

[0002] Broadband cavity-enhanced absorption spectroscopy, an optical detection technique, uses the fingerprint absorption characteristics of gas molecules to quantify gas concentrations and is widely used to detect a variety of trace gases. It uses an optical resonant cavity composed of highly reflective mirrors. The light beam is reflected multiple times by the resonant cavity. The transmitted light beam is then split by a spectrometer and received by a detector. This can increase the effective absorption pathlength to tens of thousands times the base length of the resonant cavity, resulting in very high detection sensitivity.

[0003] Broadband cavity-enhanced absorption spectroscopy systems generally consist of a light source, an optical resonant cavity, a spectrum detection unit, and a signal processing unit. The light emitted by the light source is reflected multiple times by high-reflection mirrors at both ends of the optical resonant cavity, and the light transmitted from one end of the resonant cavity is captured by the spectrum detection unit. The signal processing unit obtains the concentration of the gas to be measured by least squares inversion based on the reference lamp spectrum data when the resonant cavity is filled with zero-absorption gas and the measured absorption spectrum data when it is filled with the gas to be measured, as well as the standard absorption cross-section data of the gas to be measured.

[0004] Conventional broadband cavity enhancement algorithms rely on the absolute stability of the light source. This means that any changes in the measured absorption spectrum compared to the lamp spectrum are due to the extinction of the gas being measured. However, the reference lamp spectrum and the measured absorption spectrum are not measured simultaneously. The measured spectrum corresponds to the true, unmeasured lamp spectrum, or the original lamp spectrum, which is subject to distortion due to numerous factors, including temperature effects on the lamp source and spectrometer, and changes in light flux caused by mechanical vibration. Therefore, in addition to gas absorption information, the actual measured spectrum may also contain spectral distortions in three dimensions: intensity variations, wavelength drift, and spectral stretching / compression. These distortions can generate non-gas absorption structures during the concentration inversion, contributing to the least-squares fit and ultimately severely affecting the gas concentration inversion. Although some research groups have employed methods such as adding polynomial coefficients to the inversion process or combining differential absorption spectroscopy with broadband cavity enhancement techniques, these measures can only mitigate the influence of broadband spectral distortions. However, the narrowband structure still affects the gas concentration fit, leading to significant errors in the calculated gas concentration, and thus urgently need to be addressed. Summary of the Invention

[0005] In order to avoid and overcome the technical problems existing in the prior art, the present invention provides an interference-resistant broadband cavity-enhanced absorption spectrum inversion method, which can effectively improve the accuracy of gas concentration calculation.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] An interference-resistant broadband cavity-enhanced absorption spectrum inversion method includes the following inversion steps:

[0008] S1. Based on broadband cavity-enhanced absorption spectroscopy technology, obtain reference lamp spectrum data and measured absorption spectrum data for each channel collected by the spectrometer when the resonant cavity is filled with zero-absorbing gas and when the resonant cavity is filled with the gas to be measured. Combined with the average reflectivity of the high-reflectivity mirrors at both ends of the resonant cavity, the physical length of the resonant cavity, and the absorption cross-section of each gas to be measured, these data will be used for subsequent calculations.

[0009] S2. Input the data obtained in step S1 into the absorption coefficient calculation formula of the gas to be measured to calculate the absorption coefficient of the gas to be measured under each channel of the spectrometer;

[0010] S3. Due to the time difference between the measurement of the reference light spectrum and the measured absorption spectrum, the original light spectrum at the same time as the measured absorption spectrum cannot be directly measured because the resonant cavity is already filled with the gas to be measured. Based on the possible deformation of the original light spectrum in three dimensions relative to the reference light spectrum, the function expression of the original light spectrum is obtained;

[0011] S4, deriving a pseudo-absorption function that interferes with the measurement due to spectral deformation based on a conventional cavity-enhanced absorption spectrum inversion algorithm and the original lamp spectrum function in step S3;

[0012] S5. Combine the absorption coefficient calculation formula of the gas to be measured, the original lamp spectrum function and the pseudo absorption function to construct a gas concentration calculation formula, and input the data obtained in step S1 and the absorption coefficient obtained in step S2 into the gas concentration calculation formula in sequence to inversely calculate the gas concentration of each gas to be measured.

[0013] As a further solution of the present invention, the calculation formula of the absorption coefficient of the gas to be measured is specifically expressed as follows:

[0014] ;

[0015] Where, Indicates the gas under test is in the spectrometer n Absorption coefficient under each channel; Indicates that the spectrometer n The reference lamp spectrum data when the resonant cavity is filled with zero-absorption gas under each channel, represents the reference lamp spectrum function of zero-absorbing gas; Indicates that the spectrometer n Under each channel, the measured absorption spectrum data when the resonant cavity is filled with the gas to be measured, Represents the measured absorption spectrum function of the gas to be detected; Indicates that the high reflective mirror is in the first nThe average reflectivity of each channel at the corresponding wavelength; Represents the physical length of the resonant cavity.

[0016] As a further solution of the present invention, the original light spectrum function is specifically expressed as follows:

[0017] ;

[0018] Where, Indicates that the spectrometer n The intensity change of the original light spectrum data relative to the reference light spectrum data under each channel; Indicates that the spectrometer n The horizontal drift of the original light spectrum data relative to the reference light spectrum data under each channel; Indicates that the spectrometer n Under each channel, the original light spectrum data undergoes squeezing / stretching shape changes relative to the reference light spectrum data. In practical applications, Can exist in scalar form; Indicates that the spectrometer n Under each channel, the original light spectrum data corresponding to the actual absorption spectrum is measured. It represents the original light spectrum function corresponding to the measured absorption spectrum.

[0019] As a further solution of the present invention, the pseudo absorption function is specifically expressed as follows:

[0020] ;

[0021] Where, Indicates that the spectrometer n The pseudo absorption of the gas to be detected under each channel; Represents the pseudo absorption function of the gas to be measured.

[0022] As a further solution of the present invention: the gas concentration calculation formula is specifically expressed as follows:

[0023] ;

[0024] Where, Indicates the k The gas concentration of the gas to be measured, K Indicates the total number of gas categories to be tested; Indicates that the spectrometer n Under the channel, k The absorption cross section of the gas to be measured; represents a third-order polynomial; express Pseudo concentration.

[0025] As a further solution of the present invention, the specific steps of step S5 are as follows:

[0026] S51, define the fitting channel range in the fitting spectrometer as [ ;in, Indicates the spectrometer m Channels, that is, the starting channel number of the fitting channel range; Indicates the spectrometer M Channel, that is, the ending channel number of the fitting channel range; Indicates the total number of channels of the spectrometer;

[0027] S52, within the fitting channel range, construct the gas concentration calculation formula under each channel respectively; and combine all the constructed gas concentration calculation formulas to form a M - m An overdetermined set of equations for calculating gas concentrations;

[0028] S53. The absorption cross sections of various gases to be measured, the reference lamp spectrum data, the measured absorption spectrum data, the average reflectivity of the high-reflection mirror, and the physical length of the resonant cavity are brought into the overdetermined equations and the equations are solved to obtain the gas concentrations of the various gases to be measured.

[0029] As a further solution of the present invention: in the process of solving the overdetermined equations, Solve as a whole.

[0030] As a further solution of the present invention: in the process of solving the overdetermined equations, the nonlinear least square method is used to solve the equations.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. This invention achieves high-precision gas concentration measurement by accurately calculating measurement data from broadband cavity-enhanced absorption spectroscopy. Taking into account the impact of potential spectral distortion on the measurement results, the original lamp spectrum function is derived, and then a pseudo-absorption function is constructed to calculate the pseudo-absorption amount. This effectively corrects these errors and improves the accuracy and reliability of the measurement. From data collection to final concentration inversion, each step provides necessary information and support for the next step, ensuring the systematic and complete nature of the entire measurement process.

[0033] 2. The reference lamp spectrum data, measured when the resonant cavity is filled with zero-absorption gas, serves as a benchmark for subsequent analysis, helping to eliminate spectral variations caused by non-gas absorption factors such as light source fluctuations and instrument noise. Simultaneously, the measured absorption spectrum data, obtained when the resonant cavity is filled with the gas to be measured, directly reflects the light absorption of the gas to be measured. Accurate measurement of the high-reflectivity mirror reflectivity and the physical length of the resonant cavity is crucial for calculating the effective path length of light within the resonant cavity, which in turn affects the accuracy of the absorption coefficient calculation. The absorption cross section of each gas to be measured is the basic data for calculating the absorption coefficient, and its accuracy directly affects the final gas concentration inversion result.

[0034] 3. Using the data collected in step S1 and the absorption coefficient calculation formula, the absorption coefficient of the gas under test can be accurately calculated in each channel of the spectrometer. This is the basis for understanding gas absorption characteristics and evaluating gas concentration.

[0035] 4. A pseudo-absorption function constructed based on the original lamp spectrum function can quantify the degree of interference of spectral deformation on absorption measurement. The pseudo-absorption calculated by the pseudo-absorption function can be eliminated in the subsequent gas concentration inversion process, further improving measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the inversion flow chart of the present invention.

[0037] Figure 2 Spectrum diagram in an embodiment of the present invention.

[0038] Figure 3 This is a fitting result diagram obtained by using this method in the implementation of the present invention.

[0039] Figure 4 This is a fitting result diagram obtained by using traditional methods in the implementation of the present invention. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0041] See also Figure 1 In an embodiment of the present invention, an anti-interference broadband cavity enhanced absorption spectrum inversion method includes the following contents.

[0042] 1. Get data

[0043] Based on broadband cavity-enhanced absorption spectroscopy technology, the reference lamp spectrum data when the resonant cavity under each channel of the spectrometer is filled with zero-absorption gas, the measured absorption spectrum data when the resonant cavity is filled with the gas to be measured, the average reflectivity of the high-reflectivity mirror in the resonant cavity, the physical length of the resonant cavity, and the absorption cross-section of each gas to be measured are measured.

[0044] 1.1. Experimental setup

[0045] Resonant cavity design: Construct a high-fineness optical resonant cavity, usually composed of a pair of highly reflective mirrors. The reflectivity of the highly reflective mirrors should be as high as possible (such as 99.97% or higher) to increase the effective absorption optical path of the system.

[0046] Light source and spectrometer: Select a broadband light source (such as an LED or xenon lamp) to ensure that it covers the required wavelength range. The spectrometer is used to measure the spectral data after light passes through the resonant cavity.

[0047] Gas control system: Set up a gas control system that can accurately control and switch the gas in the resonant cavity (such as zero absorption gas and test gas).

[0048] 1.2 Data Collection

[0049] Reference lamp spectrum data: First, fill the resonant cavity with a zero-absorption gas (such as high-purity nitrogen or zero-absorption air). Then, turn on the light source and spectrometer. Record the spectral data at this time and use it as the reference lamp spectrum data. This reflects the basic performance of the resonant cavity and spectrometer system.

[0050] Measure absorption spectrum data: Subsequently, the zero-absorption gas in the resonant cavity is completely replaced with the gas to be measured, while keeping other conditions unchanged. The spectrum data is recorded again and recorded as measured absorption spectrum data, which contains the absorption characteristics of the gas to be measured.

[0051] 2.3 Resonant cavity parameter measurement

[0052] Average reflectivity of a high-reflectivity mirror: The reflectivity of a reflector can be calibrated using the Rayleigh scattering difference method, which uses the Rayleigh scattering difference between nitrogen and helium.

[0053] The physical length of the resonant cavity: Measured directly or determined using design parameters. The length affects the mode spacing and effective optical path length of the resonant cavity.

[0054] 2.4 Absorption cross-section data

[0055] Theoretical calculation or literature search: For most common gases, their absorption cross-section data can be obtained by consulting relevant literature or databases (such as HITRAN).

[0056] Experimental Calibration: If necessary, experimental calibration can be performed using standard gases of known concentration to verify or adjust the theoretical absorption cross section data.

[0057] 2.5 Data Processing and Analysis

[0058] Spectral analysis: Use spectral analysis software to process the collected spectral data and extract the absorption characteristics of the gas to be tested. In the embodiment of the present invention, each channel of the spectrometer corresponds to a wavelength range, and the number of channels of the spectrometer used is , the corresponding wavelength range is [295,415]nm.

[0059] Concentration inversion: Using the broadband cavity-enhanced absorption spectrum inversion algorithm and known resonant cavity parameters and absorption cross-section data, the concentration of the gas to be measured is inverted from the measured absorption spectrum data.

[0060] 2.6 Verification and Optimization

[0061] Repeatability test: Repeat the experiment multiple times to verify the stability and reliability of the data.

[0062] System optimization: Adjust experimental parameters (such as light source intensity, gas flow rate, resonant cavity design, etc.) based on experimental results to improve measurement accuracy and sensitivity.

[0063] Through the above steps, various measurement data based on broadband cavity-enhanced absorption spectroscopy technology can be systematically acquired and processed.

[0064] 2. Calculate the absorption coefficient of the gas to be measured

[0065] The measurement data obtained above are input into the calculation formula of the absorption coefficient of the gas to be measured as shown in formula (1), and the absorption coefficient of the gas to be measured under each channel of the spectrometer is calculated.

[0066] (1)

[0067] 3. Constructing the original light spectrum function

[0068] Based on the data obtained above, and in combination with the three possible deformations of the original light spectrum data relative to the reference light spectrum data, a deformation light spectrum function is derived.

[0069] During the spectrometer's measurement process, when the resonant cavity changes from being filled with zero-absorption gas to being filled with the gas to be measured, the measured spectral data will be distorted. The reasons for this distortion are analyzed as follows:

[0070] 1. Gas Absorption: The gas being measured absorbs light within a specific wavelength range, which causes the light intensity passing through the resonant cavity to weaken at these wavelengths. This absorption characteristic is determined by the molecular structure of the gas, and different gases have different absorption spectra.

[0071] 2. Scattering: Gas molecules may also scatter light, which changes the direction of light propagation and thus reduces the light intensity reaching the spectrometer detector.

[0072] 3. Temperature and pressure changes: If the temperature and pressure inside the resonant cavity change during the measurement, this can also cause spectral distortion. However, in precision spectral measurements, these parameters are usually controlled to keep them constant.

[0073] The discrete reference light spectrum function is interpolated by cubic spline interpolation, and then the channel number sequence after deformation is obtained. and intensity changes , we can get the deformed original light spectrum function as shown in formula (2).

[0074] (2)

[0075] 4. Constructing a pseudo absorption function

[0076] Based on the derived original light spectrum data, a pseudo absorption function is constructed to interfere with the measurement due to spectral deformation. The pseudo absorption function is shown in formula (3):

[0077] (3)

[0078] 5. Calculate the gas concentration of the gas to be measured

[0079] According to the absorption characteristics of the gas to be measured, the fitting channel range in the fitting spectrometer is defined as [ .

[0080] The absorption cross section, pseudo absorption amount, and absorption coefficient of various gases to be measured in each channel within the fitting channel range are brought into the gas concentration calculation formula shown in formula (4) to construct a gas concentration calculation formula containing M - m An overdetermined set of equations for calculating gas concentrations.

[0081] (4)

[0082] In Python environment, use the nonlinear solver in scipy library to solve the overdetermined equations, and then get the gas concentration of various gases to be measured. Solve as a whole.

[0083] 6. Examples

[0084] A 368nm broadband cavity-enhanced absorption spectroscopy system is used as an example for detailed description. The system uses an LED with a central wavelength of 368nm as the light source and a TEC temperature control module for LED temperature control. Light emitted from the LED is coupled into a resonant cavity via an achromatic lens. The cavity consists of two highly reflective mirrors. Light exiting the cavity is focused by an off-axis parabolic mirror and coupled to one end of an optical fiber. The other end of the fiber is connected to a spectrometer. A computer receives the spectral signal from the spectrometer and ultimately interprets the concentration information. This system can simultaneously measure gaseous nitrous acid (HONO) and nitrogen dioxide (NO2) in the atmosphere.

[0085] Although the system controls the temperature of the LED light source through the TEC temperature control module, in actual field observations, when encountering drastic changes in ambient temperature, such as when the instrument altitude rises during profile measurement, the LED light source will still experience temperature drift, causing spectral deformation and ultimately affecting the gas concentration inversion results.

[0086] In order to verify the actual effect of the present invention, the following experiment is first conducted: the instrument is placed in a temperature-stable environment, and the TEC temperature control module is set to maintain the temperature of the LED lamp source at 26°C. After the instrument is stabilized, nitrogen is used as a zero-absorption gas to fill the resonant cavity, and the reference lamp spectrum data (lamp-26°C) is measured. Afterwards, the temperature of the LED lamp source is set to 24°C to simulate the temperature drift of the LED light source after being disturbed by the environment. After the instrument is stabilized, another reference lamp spectrum data (lamp-24°C) is measured. After the lamp spectrum measurement is completed, air is sampled into the resonant cavity to obtain the measured absorption spectrum data of the atmosphere (data-24°C). The measured data is as follows Figure 2 As shown, it can be seen that lamp-24℃ has undergone more obvious deformation compared to lamp-26℃.

[0087] The specific steps are as follows:

[0088] 1. Prepare input data:

[0089] Get the average reflectivity of the high reflectivity mirror , the physical length of the resonant cavity , the convoluted absorption cross sections of HONO, NO2 and O4 and , using lamp-26℃ as reference lamp spectrum data , use the data-24℃ measured after LED temperature drift as the measurement absorption spectrum data .

[0090] 2. Use formula (1) to calculate the absorption coefficient of the gas to be measured .

[0091] 3. In the Python environment, use the cubic spline interpolation method in the scipy library to interpolate the reference light spectrum data and construct the deformed original light spectrum function corresponding to formula (2).

[0092] 4. Use formula (3) to construct the pseudo-absorption function that interferes with the measurement due to spectral deformation.

[0093] 5. According to the absorption characteristics of the gas and the various parameters of the instrument, determine the fitting channel range , so we get the overdetermined equations shown in formula (5):

[0094] (5)

[0095] Where, Indicates the fitting channel range of the gas to be measured in the spectrometer The absorption coefficient of each channel in . Indicates the gas concentration of the gas to be measured HONO; Indicates the fitting channel range of the spectrometer The absorption cross section of the gas HONO under each channel. Indicates the gas concentration of NO2 to be measured; Indicates the fitting channel range of the spectrometer The absorption cross section of the test gas NO2 in each channel. Indicates the gas concentration of O4 to be measured; Indicates the fitting channel range of the spectrometer The absorption cross section of the gas O4 to be measured in each channel. a 、 b, c, d are are the polynomial coefficients. Indicates the fitting channel range of the spectrometer The horizontal drift of the original light spectrum data relative to the reference light spectrum data in each channel. Indicates the fitting channel range of the spectrometer The squeezing / stretching shape changes of the original light spectrum data relative to the reference light spectrum data in each channel. Indicates the fitting channel range of the spectrometer In each channel, the intensity change of the original light spectrum data relative to the reference light spectrum data occurs. In this embodiment, For different The values ​​are the same.

[0096] In the Python environment, use the curve_fit tool in the scipy library to solve the gas concentration of the gas to be measured. and , the inversion results are as follows Figure 3As shown, it can be seen that the overall fitting effect is good, the residual is small and there is no obvious structure.

[0097] In order to verify the effectiveness of the anti-interference cavity-enhanced inversion algorithm proposed in this paper, the traditional cavity-enhanced inversion algorithm is used. Under the same fitting channel, lamp-26℃ is still used as the reference lamp spectrum to invert data-24℃. The results are as follows: Figure 4 As shown in Figure 2, the residuals become larger and have an obvious structure, and the fitting of HONO is obviously abnormal.

[0098] Based on the acquired measurement data and combined with the deformation of the original light spectrum data relative to the reference light spectrum data, the deformed light spectrum function is derived, and the deformed light spectrum data of the gas to be detected in each channel of the spectrometer is calculated using the deformed light spectrum function.

[0099] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. An anti-interference broadband cavity-enhanced absorption spectrum inversion method, characterized in that: The inversion steps include: S1. Based on broadband cavity-enhanced absorption spectroscopy technology, obtain reference lamp spectrum data and measured absorption spectrum data for each channel collected by the spectrometer when the resonant cavity is filled with zero-absorbing gas and when the resonant cavity is filled with the gas to be measured. Combined with the average reflectivity of the high-reflectivity mirrors at both ends of the resonant cavity, the physical length of the resonant cavity, and the absorption cross-section of each gas to be measured, these data will be used for subsequent calculations. S2. Input the data obtained in step S1 into the absorption coefficient calculation formula of the gas to be measured to calculate the absorption coefficient of the gas to be measured under each channel of the spectrometer; S3. Due to the time difference between the measurement of the reference light spectrum and the measured absorption spectrum, the original light spectrum at the same time as the measured absorption spectrum cannot be directly measured because the resonant cavity is already filled with the gas to be measured. Based on the possible deformation of the original light spectrum in three dimensions relative to the reference light spectrum, the function expression of the original light spectrum is obtained; S4, deriving a pseudo-absorption function that interferes with the measurement due to spectral deformation based on a conventional cavity-enhanced absorption spectrum inversion algorithm and the original lamp spectrum function in step S3; S5. Combine the absorption coefficient calculation formula of the gas to be measured, the original lamp spectrum function, and the pseudo absorption function to construct a gas concentration calculation formula, and input the data obtained in step S1 and the absorption coefficient obtained in step S2 into the gas concentration calculation formula in sequence to inversely calculate the gas concentration of each gas to be measured; The calculation formula of the absorption coefficient of the gas to be measured is specifically expressed as follows: ； Where, Indicates the gas under test is in the spectrometer n Absorption coefficient under each channel; Indicates that the spectrometer n The reference lamp spectrum data when the resonant cavity is filled with zero-absorption gas under each channel, represents the reference lamp spectrum function of zero-absorbing gas; Indicates that the spectrometer n Under each channel, the measured absorption spectrum data when the resonant cavity is filled with the gas to be measured, Represents the measured absorption spectrum function of the gas to be measured; Indicates that the high reflective mirror is in the first n The average reflectivity of each channel at the corresponding wavelength; represents the physical length of the resonant cavity; The original light spectrum function is specifically expressed as follows: ； Where, Indicates that the spectrometer n The intensity change of the original light spectrum data relative to the reference light spectrum data under each channel; Indicates that the spectrometer n The horizontal drift of the original light spectrum data relative to the reference light spectrum data under each channel; Indicates that the spectrometer n The horizontal drift shape change of the original light spectrum data relative to the reference light spectrum data under each channel; Indicates that the spectrometer n Under each channel, the original light spectrum data corresponding to the actual absorption spectrum is measured. Indicates the original light spectrum function corresponding to the measured absorption spectrum; The pseudo absorption function is specifically expressed as follows: ； Where, Indicates that the spectrometer n The pseudo absorption amount of the gas to be detected during inversion under each channel; represents the pseudo absorption function during the inversion of the gas to be detected; The gas concentration calculation formula is as follows: ； Where, Indicates the k The gas concentration of the gas to be measured, K Indicates the total number of gas categories to be tested; Indicates that the spectrometer n Under the channel, k The absorption cross section of the gas to be measured; represents a third-order polynomial; express Pseudo concentration.

2. The anti-interference broadband cavity-enhanced absorption spectrum inversion method according to claim 1, characterized in that: The specific steps of step S5 are as follows: S51, define the fitting channel range in the fitting spectrometer as [ ;in, Indicates the spectrometer m Channels, that is, the starting channel number of the fitting channel range; Indicates the spectrometer M Channel, that is, the ending channel number of the fitting channel range; Indicates the total number of channels of the spectrometer; S52, within the fitting channel range, construct the gas concentration calculation formula under each channel respectively; and combine all the constructed gas concentration calculation formulas to form a M - m An overdetermined set of equations for calculating gas concentrations; S53. Substitute the absorption cross sections of various gases to be measured, reference lamp spectrum data, measured absorption spectrum data, the average reflectivity of the high-reflection mirror, and the physical length of the resonant cavity into the overdetermined equations and solve them to obtain the gas concentrations of various gases to be measured.

3. The anti-interference broadband cavity-enhanced absorption spectrum inversion method according to claim 2, characterized in that: In the process of solving the overdetermined system of equations, Solve as a whole.

4. The anti-interference broadband cavity-enhanced absorption spectrum inversion method according to claim 3, characterized in that: In the process of solving overdetermined equations, the nonlinear least squares method is used to solve the equations.

Images