Anti-interference broadband cavity enhanced absorption spectrum inversion algorithm

Abstract

The invention relates to the technical field of gas concentration calculation, in particular to an anti-interference broadband cavity enhanced absorption spectrum inversion algorithm. On the basis of a traditional cavity enhanced absorption spectrum algorithm, a pseudo-absorption function is constructed and used for representing a non-gas absorption structure caused by lamp spectrum deformation in the gas concentration inversion process, so that interference caused by lamp spectrum deformation is separated from the gas absorption structure, and the gas concentration inversion accuracy is improved. The influence of lamp spectrum deformation on a gas concentration inversion result is effectively avoided, the dependence of a traditional cavity enhancement algorithm on the absolute stability of a light source is overcome, and the gas concentration can be accurately quantified. According to the method, the robustness and environmental adaptability of the broadband cavity enhanced absorption spectrum system can be effectively improved.

Description

Technical Field

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

[0002] Broadband cavity enhanced absorption spectroscopy is an optical detection technology that uses the fingerprint absorption characteristics of gas molecules to quantify gas concentrations and is widely used in the detection of various trace gases. It uses an optical resonant cavity composed of high-reflection mirrors. The light beam is reflected multiple times by the resonant cavity, and the transmitted light beam is received by the detector after being split by the spectrometer. It can increase the effective absorption optical path to tens of thousands of times the base length of the resonant cavity, and has a high detection sensitivity.

[0003] Broadband cavity enhanced absorption spectroscopy systems are generally composed 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 inverting the reference lamp spectrum data when the resonant cavity is filled with zero-absorption gas, the measured absorption spectrum data when the resonant cavity is filled with the gas to be measured, and the standard absorption cross-section data of the gas to be measured through the least squares method.

[0004] The traditional broadband cavity enhancement algorithm relies on the absolute stability of the light source, that is, the changes in the measured absorption spectrum compared to the lamp spectrum are all caused by the extinction effect of the gas to be measured. However, the reference lamp spectrum and the measured absorption spectrum are not measured at the same time. The real and unmeasurable lamp spectrum corresponding to the measured spectrum, that is, the original lamp spectrum, is actually affected by many factors and deformed, including the influence of temperature on the lamp source and spectrometer, and the change of light flux caused by mechanical vibration. Therefore, in addition to the absorption information of the gas, the actual measured spectrum may also contain spectral deformation information from three dimensions: intensity change, wavelength drift, and spectral stretching / compression. These deformations will produce non-gas absorption structures during concentration inversion, participate in least squares fitting, and ultimately have a serious impact on the inversion of gas concentration. Although some research groups have adopted the method of adding polynomial coefficients in the inversion process, or combined differential absorption spectroscopy with broadband cavity enhancement technology, these measures can only reduce the influence of broadband structures in spectral deformation, while the narrowband structure will still affect the gas concentration fitting, resulting in large errors in the calculation results of gas concentration, so it needs to be solved urgently. Summary of the invention

[0005] In order to avoid and overcome the technical problems existing in the prior art, the present invention provides an anti-interference broadband cavity enhanced absorption spectrum inversion algorithm. The present invention 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 anti-interference broadband cavity enhanced absorption spectrum inversion algorithm includes the following inversion steps:

[0008] S1. Based on broadband cavity enhanced absorption spectroscopy technology, the reference lamp spectrum data and measured absorption spectrum data of each channel collected by the spectrometer when the resonant cavity is filled with zero-absorption gas and the resonant cavity is filled with the gas to be measured are obtained respectively, combined with the average reflectivity of the high-reflection 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, for subsequent calculation and use;

[0009] S2, inputting the data obtained in step S1 into the calculation formula of the absorption coefficient of the gas to be measured, and calculating the absorption coefficient of the gas to be measured under each channel of the spectrometer;

[0010] S3. Since there is a time difference between the measurement of the reference light spectrum and the measured absorption spectrum, the original light spectrum at the same time corresponding to the measured absorption spectrum cannot be directly measured because the resonant cavity is already filled with the gas to be measured; according to 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, according to the traditional cavity enhanced absorption spectrum inversion algorithm and the original lamp spectrum function in step S3, deriving the pseudo absorption function that interferes with the measurement due to the spectrum deformation;

[0012] S5. Combine the absorption coefficient calculation formula of the gas to be tested, 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 tested.

[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] Wherein, α(n) represents the absorption coefficient of the gas to be tested in the nth channel of the spectrometer; I0(n) represents the reference lamp spectrum data when the resonant cavity is filled with zero-absorption gas in the nth channel of the spectrometer, and I0(·) represents the reference lamp spectrum function of zero-absorption gas; I(n) represents the measured absorption spectrum data when the resonant cavity is filled with the gas to be tested in the nth channel of the spectrometer, and I(·) represents the measured absorption spectrum function of the gas to be tested; R(n) represents the average reflectivity of the high-reflection mirror at the wavelength corresponding to the nth channel of the spectrometer; d 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] I0'(n,i n,shift ,i n,squeeze ,i n,scale )=i n,scale ·I0(i n,shift +i n,squeeze n);

[0018] In the formula, i n,scale Indicates the intensity change of the original light spectrum data relative to the reference light spectrum data under the nth channel of the spectrometer; i n,shift Indicates the horizontal drift of the original light spectrum data relative to the reference light spectrum data under the nth channel of the spectrometer; i n,squeeze Indicates the squeezing / stretching shape change of the original light spectrum data relative to the reference light spectrum data under the nth channel of the spectrometer. In practical applications, i n,shift ,i n,squeeze ,i n,scale Can exist in the form of a scalar; I0'(n,i n,shift ,i n,squeeze , i n ,scale ) represents the original light spectrum data corresponding to the measured absorption spectrum under the nth channel of the spectrometer, and I0'(·) 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] In the formula, st(n,i n,shift ,i n,squeeze ,i n,scale ) represents the pseudo absorption of the gas to be detected under the nth channel of the spectrometer; st(·) represents the pseudo absorption function of the gas to be detected.

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

[0023]

[0024] In the formula, c k represents the gas concentration of the kth gas to be tested, K represents the total number of gas types to be tested; σ k (n) represents the absorption cross section of the kth gas to be measured under the nth channel of the spectrometer; p represents a third-order polynomial; c0 represents st(n,i n,shift ,i n,squeeze ,i n,scale )’s 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 [n m ,n M ]∈[0,N-1]; where n m Indicates the mth channel of the spectrometer, that is, the starting channel number of the fitting channel range; n M Indicates the Mth channel of the spectrometer, that is, the ending channel number of the fitting channel range; N indicates the total number of channels of the spectrometer;

[0027] S52, within the fitting channel range, constructing gas concentration calculation formulas for each channel respectively; and combining all the constructed gas concentration calculation formulas to form an overdetermined equation group including Mm gas concentration calculation formulas;

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

[0029] As a further solution of the present invention: in the process of solving the overdetermined system of equations, c0·st(n,i n,shift ,i n,squeeze ,i n,scale ) is solved as a whole.

[0030] As a further solution of the present invention: in the process of solving the overdetermined system of 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. The present invention can achieve high-precision measurement of gas concentration by accurately calculating the measurement data of broadband cavity enhanced absorption spectroscopy. Taking into account the influence of spectral deformation that may exist in spectral measurement on the measurement results, the pseudo-absorption amount is calculated by deriving the original lamp spectrum function and then constructing a pseudo-absorption function, which effectively corrects these errors and improves the accuracy and reliability of the measurement. From the whole process of data collection to the final concentration inversion, each step provides the necessary information and support for the next step, ensuring the systematicness and integrity 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 the basis for subsequent analysis, helping to eliminate spectral changes caused by non-gas absorption factors such as light source fluctuations and instrument noise. At the same time, the measured absorption spectrum data measured when the resonant cavity is filled with the gas to be measured directly reflects the absorption of light by the gas to be measured. Accurate measurement of the reflectivity of the high-reflection mirror and the physical length of the resonant cavity is crucial for calculating the effective path length of light in the resonant cavity, which in turn affects the calculation accuracy of the absorption coefficient. 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 inversion result of the final gas concentration.

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

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

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

[0037] Figure 2 It is a spectrum diagram in an embodiment of the present invention.

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

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

[0040] 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.

[0041] See also Figure 1 In an embodiment of the present invention, an anti-interference broadband cavity enhanced absorption spectrum inversion algorithm 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-reflection 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 device construction

[0045] Resonant cavity design: Build 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 LED, xenon lamp, etc.) to ensure that the required wavelength range is covered. The spectrometer is used to measure the spectral data after the light passes through the resonant cavity.

[0047] Gas control system: A gas control system is set up to accurately control and switch the gas in the resonant cavity (such as zero absorption gas and gas to be measured).

[0048] 1.2 Data Collection

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

[0050] Measuring absorption spectrum data: Subsequently, the zero-absorption gas in the resonant cavity is completely replaced with the gas to be measured, and other conditions are kept unchanged. The spectrum data is recorded again and recorded as measured absorption spectrum data, which includes 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 by using the Rayleigh scattering difference method, which uses the Rayleigh scattering difference between nitrogen and helium.

[0053] Physical length of the resonant cavity: Measured directly or determined using design parameters. The length will affect 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 ranges from [0,1043], and 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 can be inverted from the measured absorption spectrum data.

[0060] 2.6 Verification and Optimization

[0061] Repeatability test: Repeat the experiment several 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.) according to 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 absorption coefficient calculation formula 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]

[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 measurement process of the spectrometer, 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 deformed. The reasons for this deformation are analyzed as follows:

[0070] 1. Gas absorption: The gas to be 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 will change the direction of light propagation and thus reduce the light intensity reaching the spectrometer detector.

[0072] 3. Temperature and pressure changes: If the temperature and pressure in the resonant cavity change during the measurement, it may also cause the spectrum to be deformed. However, in precision spectral measurements, these parameters are usually controlled as much as possible to keep them constant.

[0073] The discrete reference light spectrum function is interpolated by cubic spline interpolation, and then the channel number sequence n'=i after deformation is calculated. n,shift +i n,squeeze n and intensity variation i n,scale , we can get the deformed original light spectrum function as shown in formula (2).

[0074] I0'(n,i n,shift ,i n,squeeze ,i n,scale )=i n,scale ·I0(i n,shift +i n,squeeze ·n) (2)

[0075] 4. Constructing a pseudo absorption function

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

[0077]

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

[0079] According to the absorption characteristics of the gas to be measured, the fitting channel range in the fitting spectrometer is defined as [n m ,n M ]∈[0,N-1].

[0080] The absorption cross sections, pseudo-absorption amounts, and absorption coefficients of various gases to be measured in each channel within the fitting channel range are substituted into the gas concentration calculation formula shown in formula (4) to construct an overdetermined equation group containing Mm gas concentration calculation equations.

[0081]

[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. n,shift ,i n,squeeze ,in,scale ) is solved as a whole.

[0083] 6. Embodiment

[0084] The 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 uses a TEC temperature control module to control the temperature of the LED. The output light of the LED is coupled into the resonant cavity by an achromatic lens. The resonant cavity is composed of two highly reflective mirrors. The light transmitted from the resonant cavity is focused by an off-axis parabolic mirror and coupled to one end of the optical fiber. The other end of the optical fiber is connected to a spectrometer. The computer receives the spectral signal through the spectrometer and finally inverts the concentration information. The 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 the ambient temperature changes drastically, such as when the instrument altitude rises when measuring the profile, the LED light source will still experience temperature drift, causing the spectrum to deform, ultimately affecting the gas concentration inversion results.

[0086] In order to verify the actual effect of the present invention, the following experiment is first carried out: the instrument is placed in a temperature-stable environment, and the TEC temperature control module is set to maintain the temperature of the LED light source at 26°C. After the instrument is stabilized, nitrogen is used as the zero-absorption gas to fill the resonant cavity, and the reference light spectrum data (lamp-26°C) is measured. Afterwards, the temperature of the LED light 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 light spectrum data (lamp-24°C) is measured. After the light spectrum measurement is completed, the 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 R(n) of the high-reflectivity mirror, the physical length d of the resonant cavity, and the convolved absorption cross sections σ of HONO, NO2, and O4 HONO (n) and Use lamp-26℃ as the reference lamp spectrum data I0(n), use data-24℃ measured after LED temperature drift as the measured absorption spectrum data I(n), and this system uses the spectrometer serial number n=0,1,2,…,1043.

[0090] 2. Use formula (1) to calculate the absorption coefficient α(n) 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 as n fit =550,551,…,780, so we get the overdetermined equations as shown in formula (5):

[0094]

[0095] In the formula, α(n fit ) represents the fitting channel range n of the gas to be measured in the spectrometer fit The absorption coefficient of each channel in the HONO Indicates the gas concentration of the gas HONO to be measured; σ HONO (n fit ) represents the fitting channel range n of the spectrometer fit The absorption cross section of the gas HONO under each channel. Indicates the gas concentration of NO2 to be tested; Indicates the fitting channel range n of the spectrometer ift The absorption cross section of the measured gas NO2 in each channel. Indicates the gas concentration of O4 to be measured; Indicates the fitting channel range n of the spectrometer ift The absorption cross section of the gas O4 under each channel. a, b, c, d are all polynomial coefficients. Indicates the fitting channel range n of the spectrometer ift The horizontal drift of the original light spectrum data relative to the reference light spectrum data in each channel. Indicates the fitting channel range n of the spectrometer ift 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 n of the spectrometer ift 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 n ift The values ​​are the same.

[0096] In Python environment, use the curve_fit tool in the scipy library to solve and get the gas concentration c of the gas to be measured. HONO and The inversion results are as follows Figure 3 As 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 invention, 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, 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 implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An anti-interference broadband cavity enhanced absorption spectrum inversion algorithm, characterized in that: The inversion steps include: S1. Based on broadband cavity enhanced absorption spectroscopy technology, the reference lamp spectrum data and measured absorption spectrum data of each channel collected by the spectrometer when the resonant cavity is filled with zero-absorption gas and the resonant cavity is filled with the gas to be measured are obtained respectively, combined with the average reflectivity of the high-reflection 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, for subsequent calculation and use; S2, inputting the data obtained in step S1 into the calculation formula of the absorption coefficient of the gas to be measured, and calculating the absorption coefficient of the gas to be measured under each channel of the spectrometer; S3. Since there is a time difference between the measurement of the reference light spectrum and the measured absorption spectrum, the original light spectrum at the same time corresponding to the measured absorption spectrum cannot be directly measured because the resonant cavity is already filled with the gas to be measured; according to 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, according to the traditional cavity enhanced absorption spectrum inversion algorithm and the original lamp spectrum function in step S3, deriving the pseudo absorption function that interferes with the measurement due to the spectrum deformation; S5. Combine the absorption coefficient calculation formula of the gas to be tested, 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 tested.

2. The anti-interference broadband cavity enhanced absorption spectrum inversion algorithm according to claim 1, characterized in that: The calculation formula of the absorption coefficient of the gas to be measured is specifically expressed as follows: Wherein, α(n) represents the absorption coefficient of the gas to be measured in the nth channel of the spectrometer; I0(n) represents the reference lamp spectrum data when the resonant cavity is filled with zero absorption gas in the nth channel of the spectrometer, and I0(·) represents the reference lamp spectrum function of the zero absorption gas; I(n) represents the measured absorption spectrum data when the resonant cavity is filled with the gas to be measured under the nth channel of the spectrometer, I(·) represents the measured absorption spectrum function of the gas to be measured; R(n) represents the average reflectivity of the high-reflection mirror at the wavelength corresponding to the nth channel of the spectrometer; d represents the physical length of the resonant cavity.

3. The anti-interference broadband cavity enhanced absorption spectrum inversion algorithm according to claim 2, characterized in that: The original light spectrum function is specifically expressed as follows: I0'(n,i n,shift ,i n,squeeze ,i n,scale )=i n,scale ·I0(i n,shift +i n,squeeze ·n); In the formula, i n,scale Indicates the intensity change of the original light spectrum data relative to the reference light spectrum data under the nth channel of the spectrometer; i n,shift Indicates the horizontal drift of the original light spectrum data relative to the reference light spectrum data under the nth channel of the spectrometer; i n,squeeze Indicates the horizontal drift shape change of the original light spectrum data relative to the reference light spectrum data under the nth channel of the spectrometer; I0'(n,i n,shift ,i n,squeeze ,i n,scale ) represents the original light spectrum data corresponding to the measured absorption spectrum under the nth channel of the spectrometer, and I0'(·) represents the original light spectrum function corresponding to the measured absorption spectrum.

4. The anti-interference broadband cavity enhanced absorption spectrum inversion algorithm according to claim 3, characterized in that: The pseudo absorption function is specifically expressed as follows: In the formula, st(n,i n,shift ,i n,squeeze ,i n,scale ) represents the pseudo absorption of the gas to be detected during inversion under the nth channel of the spectrometer; st(·) represents the pseudo absorption function of the gas to be detected during inversion.

5. The anti-interference broadband cavity enhanced absorption spectrum inversion algorithm according to claim 4, characterized in that: The gas concentration calculation formula is specifically expressed as follows: In the formula, c k represents the gas concentration of the kth gas to be tested, K represents the total number of gas types to be tested; σ k (n) represents the absorption cross section of the kth gas to be measured under the nth channel of the spectrometer; p represents a third-order polynomial; c0 represents st(n,i n,shift ,i n,squeeze ,i n,scale )’s pseudo concentration.

6. The anti-interference broadband cavity enhanced absorption spectrum inversion algorithm according to claim 5, characterized in that: The specific steps of step S5 are as follows: S51, define the fitting channel range in the fitting spectrometer as [n m ,n M ]∈[0,N-1]; where n m Indicates the mth channel of the spectrometer, that is, the starting channel number of the fitting channel range; n M Indicates the Mth channel of the spectrometer, that is, the ending channel number of the fitting channel range; N indicates the total number of channels of the spectrometer; S52, within the fitting channel range, constructing gas concentration calculation formulas for each channel respectively; and combining all the constructed gas concentration calculation formulas to form an overdetermined equation group including Mm gas concentration calculation formulas; S53. Substitute the absorption cross sections of various gases to be tested, 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 equation group and solve the equations to obtain the gas concentrations of various gases to be tested.

7. The anti-interference broadband cavity enhanced absorption spectrum inversion algorithm according to claim 6, characterized in that: In the process of solving the overdetermined system of equations, c0·st(n,i n,shift ,i n,squeeze ,i n,scale ) is solved as a whole.

8. The anti-interference broadband cavity enhanced absorption spectrum inversion algorithm according to claim 7, characterized in that: In the process of solving overdetermined equations, the nonlinear least square method is used to solve the equations.

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