A method for spectral and radiometric calibration of a spectrometer

Abstract

The present application relates to the technical field of spectrometer calibration, and particularly relates to a spectrometer spectral calibration and radiation calibration method. The technical scheme comprises spectral calibration and radiation calibration. The spectral calibration comprises the following steps: firstly, using a standard light source to perform initial spectral calibration on an uncalibrated spectrometer to obtain an initial spectral calibration equation; secondly, obtaining optical differential thickness data through a sample gas measurement experiment and combining standard gas absorption cross-section data to calculate a wavelength difference value to correct the initial spectral calibration equation to obtain a final spectral calibration equation. The present application improves the absolute error accuracy of the wavelength after spectral calibration by nearly one order of magnitude, greatly reduces the radiation calibration error, significantly improves the stability and accuracy of the radiation calibration, effectively solves the problems of limited spectral lines, poor light source stability and large extrapolation error of the traditional calibration method, and provides a solid guarantee for the high-precision application of the spectrometer in the fields of environmental monitoring, material science, remote sensing technology and the like.

Description

Technical Field

[0001] This invention relates to the field of spectrometer calibration technology, and in particular to a method for spectrometer spectral calibration and radiometric calibration. Background Technology

[0002] In recent years, spectroscopy technology has developed rapidly, and its applications have gradually expanded from the laboratory to the integrated field of space, air, and ground. Specifically, in the field of Earth observation and remote sensing, it is used for environmental monitoring (such as atmospheric composition, greenhouse gas, and water pollution detection), resource exploration (such as mineral exploration and agricultural resource assessment), and disaster early warning (such as forest fire monitoring and red tide early warning); in the field of deep space exploration and astrophysics, it is used to determine the atmospheric composition of exoplanets and study the chemical evolution of stars and galaxies; in the industrial and defense fields, it is used for materials analysis, military target identification, and biochemical detection; and in the field of basic scientific research, it is used for research in quantum optics, molecular spectroscopy, and other fields.

[0003] As the core equipment of spectroscopy, the spectrometer's function is to decompose complex light signals into different wavelength components and measure spectral data. However, during the manufacturing and use of spectrometers, systematic errors are introduced, causing deviations between the raw output (such as pixel values ​​and digital signals) and the actual physical quantities (such as wavelength and radiance). Calibration essentially establishes a precise correspondence between these two values. High-precision calibration is a core prerequisite for ensuring the accuracy, reliability, and scientific value of spectrometer measurement data, directly determining the effectiveness of spectroscopy in various fields.

[0004] Spectrometer calibration mainly includes two key steps: spectral calibration and radiometric calibration.

[0005] Spectral calibration: By using regression analysis in mathematical statistics to establish the functional relationship between the detector pixel number and wavelength, it is the basis for determining the spectral characteristics of the spectrometer system. It not only provides the necessary premise for radiometric calibration, but also directly affects the reliability of the spectrometer measurement data.

[0006] Radiometric calibration: Determining the quantitative relationship between the digital output of the detector unit and the received radiation intensity can clarify the radiation response capability of the spectrometer in different bands. It is a key step in quantitatively acquiring radiation information of ground objects and inferring the radiation characteristics of ground objects.

[0007] Currently, researchers both domestically and internationally have conducted extensive research on spectrometer calibration. Internationally, Quintus et al. performed pre-launch calibration of the TROPOMI payload aboard the Sentinel-5 satellite, ensuring the accuracy of TROPOMI onboard data. Carly Staebell et al. conducted detailed spectral calibration of the spectrometer in MethaneAIR, the simulated airborne product of the MethaneSAT satellite, including stray light correction, spectral response function acquisition, and Savitzky-Golay smoothing filtering, laying the foundation for the successful launch of the MethaneSAT satellite. Domestically, Qi Xiangdong et al. at the Changchun Institute of Optics and Fine Mechanics designed a spectral calibration system composed of a monochromator and a collimator, completing the spectral calibration of a convex grating imaging spectrometer, which has guiding significance for the calibration of dispersive imaging spectrometers. Zhou Haijin, Zhao Minjie, Yan Ge, and others at the Anhui Institute of Optics and Fine Mechanics completed the spectral and radiometric calibrations of the onboard atmospheric trace gas differential absorption spectrometers (EMI-01 and EMI-02), respectively, providing support for spectrometer remote sensing inversion work.

[0008] However, traditional calibration methods have revealed significant shortcomings when facing the current demands for high-precision applications:

[0009] Traditional spectral calibration relies on standard lamps (such as mercury lamps and argon lamps). These standard lamps have a limited number of spectral lines and fixed spectral line intensities, making it difficult to cover the fine wavelength calibration requirements of the entire measurement band of the spectrometer. This results in low accuracy of the spectral calibration results and directly increases the error of the spectrometer measurement data.

[0010] Traditional radiometric calibration uses standard lamps (such as halogen tungsten lamps) which suffer from stability decay over time, and their spectral shape differs significantly from that of the actual target (such as sunlight). During calibration, extrapolation is required to match the spectral characteristics of the target, which can easily introduce extrapolation errors. In addition, traditional radiometric calibration uses a direct division method to calculate the calibration factor, and the accuracy of the calibration results is greatly affected by the stability of the light source. Furthermore, it lacks good scalability when the measured light intensity is high, further limiting the calibration accuracy.

[0011] In summary, the stability and accuracy of existing spectrometer calibration methods are no longer sufficient to meet the demands for high-accuracy spectral data in fields such as environmental monitoring, materials science, and remote sensing. There is an urgent need to propose a new method for spectrometer spectral and radiometric calibration to address the shortcomings of traditional methods, improve calibration accuracy and stability, and ensure the high-precision application of spectroscopic technology. Therefore, this application proposes a method for spectrometer spectral and radiometric calibration. Summary of the Invention

[0012] The purpose of this invention is to address the problem that the stability and accuracy of existing spectrometer calibration methods in the background art can no longer meet the needs of high-accuracy spectral data in fields such as environmental monitoring, materials science, and remote sensing technology, and to propose a spectrometer spectral calibration and radiometric calibration method.

[0013] The technical solution of the present invention: a method for spectral calibration and radiometric calibration of a spectrometer, comprising the following steps;

[0014] Spectral calibration involves first using a standard light source to perform initial spectral calibration on the uncalibrated spectrometer to obtain an initial spectral calibration equation. Then, optical differential thickness data is obtained through sample gas measurement experiments, and combined with standard gas absorption cross-section data, the wavelength difference is calculated to correct the initial spectral calibration equation, resulting in the final spectral calibration equation.

[0015] Radiometric calibration involves measuring the spectral response data of a variable intensity light source using a spectrometer that has undergone spectral calibration at a fixed integration time. This data is then combined with standard radiance measurement data to perform linear fitting to obtain the radiometric calibration factor. The radiometric calibration factor is then corrected based on the actual integration time, and the radiance is calculated after calibration by substituting it into the radiometric calibration formula.

[0016] Optionally, in the spectral calibration step, the initial spectral calibration of the uncalibrated spectrometer using a standard light source to obtain the initial spectral calibration equation is specifically as follows: a standard lamp is used as the standard light source, which can be any one of a mercury lamp, argon lamp, or xenon lamp. By measuring the spectral lines of the standard lamp, regression analysis is performed on the spectral line peaks and the detector pixel ordinal numbers to obtain the initial spectral calibration equation.

[0017] Optionally, the spectral calibration step, in which optical differential thickness data is obtained through sample gas measurement experiments, specifically includes the following steps:

[0018] A gas with an absorption peak within the measurement band of the spectrometer is selected as the sample gas, and the sample gas includes methane;

[0019] Using a spectrometer that has undergone initial spectral calibration, the spectra of the sample gas cell were measured when nitrogen gas was introduced and when the sample gas was being tested. Differential absorption spectroscopy (DOAS) was used to process the measurement data, and the results were analyzed based on the Lambert-Beer law using the formula... Calculate optical differential thickness data; where, The measurement spectrum is for nitrogen filling. The measurement spectrum is obtained when the sample gas is filled. For the sample gas to be tested at wavelength Absorption cross section at the location, This represents the slant column density of the sample gas to be tested (SCD Slant Column Density). This refers to the smoothing effect of all non-differential absorptions, including Mie scattering, Rayleigh scattering, and broadband absorption.

[0020] Optionally, in the spectral calibration step, combining the standard gas absorption cross section data specifically involves: downloading the gas absorption cross section data corresponding to the sample gas from the HITRAN database as the standard gas absorption cross section data.

[0021] Optionally, the spectral calibration step, specifically calculating the wavelength difference to correct the initial spectral calibration equation, includes the following steps:

[0022] A. Perform convolution and sampling processing on the optical differential thickness data and the gas absorption cross section data to match the wavelength interval and number of data points between the two, ensuring consistent resolution;

[0023] B. The processed data is analyzed using a peak-finding algorithm, which includes a Gaussian function fitting method. The center wavelength of the absorption peak is determined by performing Gaussian fitting on the absorption peak, and the wavelength difference corresponding to the absorption peaks of the same gas is calculated.

[0024] C. Substitute the wavelength difference into the initial spectral calibration equation, correct the initial spectral calibration equation, and obtain the final spectral calibration equation.

[0025] Optionally, in the radiometric calibration step, measuring the spectral response data of a variable intensity light source using a spectrometer that has completed spectral calibration at a fixed integration time specifically includes: using an integrating sphere as a variable intensity light source, setting the fixed integration time of the spectrometer to X ms, changing the light source intensity by adjusting the number of lamps inside the integrating sphere, wherein the adjustment of the number of lamps covers at least two different levels, including 1 lamp, 2 lamps, 3 lamps, and 4 lamps, and measuring the spectral response data of the spectrometer at different intensities respectively.

[0026] Optionally, in the radiometric calibration step, the radiometric calibration factor is obtained by performing linear fitting with standard radiance measurement data as follows: The radiance data of the integrating sphere light source at different lamp counts is measured using a linear measuring instrument and used as standard radiance measurement data; at each wavelength, the spectral response data corresponding to the same wavelength is linearly fitted with the standard radiance measurement data. The linear fitting uses the least squares method, and the fitting slope α and intercept β are determined through linear regression analysis. The slope α and intercept β are used as the radiometric calibration factor at a fixed integration time X ms.

[0027] Optionally, in the radiometric calibration step, the radiometric calibration factor is corrected according to the actual integration time, and the radiance after calibration is calculated by substituting it into the radiometric calibration formula. Specifically, when the integration time T during actual measurement is inconsistent with the fixed integration time X ms, the slope α in the radiometric calibration factor is corrected by the proportionality coefficient T / X; the corrected slope, intercept β, and the actual measured response value N(λ) of the spectrometer are substituted into the radiometric calibration formula L(λ)=(T / X)×α×N(λ)+β to calculate the radiance after calibration L(λ).

[0028] Optionally, the spectrometer includes any one of a short-wave infrared spectrometer, an ultraviolet spectrometer, and a linear spectrometer.

[0029] Optionally, when the spectrometer is a short-wave infrared spectrometer, its spectral range is 1595nm~1675nm, and the sample gas in the spectral calibration step is methane.

[0030] Compared with the prior art, this application includes at least one of the following beneficial technical effects:

[0031] By introducing a secondary correction mechanism based on gas absorption spectral lines from a standard database, the limitations of the traditional standard lamp spectral lines—limited and fixed—are effectively overcome, improving wavelength calibration accuracy by an order of magnitude and significantly reducing the spectrometer's systematic error.

[0032] This invention uses an intensity-adjustable standard radiation source (such as an integrating sphere) and a high-precision reference radiometer for multi-point linear fitting, replacing the traditional calibration method using a single standard lamp. This effectively eliminates extrapolation errors introduced by the attenuation of the standard light source itself and spectral mismatch, and significantly improves the accuracy and long-term stability of radiation calibration.

[0033] This invention uses high-precision spectral calibration as a prerequisite for radiometric calibration, and the two are closely integrated to form a complete and optimized calibration process. This method does not depend on a specific light source or gas and can be widely applied to different bands and types of spectrometers from ultraviolet to infrared, exhibiting strong versatility and portability.

[0034] This invention improves the absolute wavelength error accuracy of spectral calibration by nearly an order of magnitude by combining gas absorption cross-section data from the HITRAN database with traditional spectral calibration, and correcting the calibration equation through convolution sampling and peak finding algorithms. Simultaneously, by using an integrating sphere as the light source and combining it with a linear measuring instrument for radiometric calibration, and correcting the calibration factor through integration time, it significantly reduces radiometric calibration errors and substantially improves the stability and accuracy of radiometric calibration. This effectively solves the problems of limited spectral lines, poor light source stability, and large extrapolation errors inherent in traditional calibration methods, providing a solid guarantee for the high-precision application of spectrometers in environmental monitoring, materials science, remote sensing technology, and other fields. Attached Figure Description

[0035] Figure 1 This is a flowchart of the spectrometer calibration method of the present invention;

[0036] Figure 2 This is a flowchart of the radiation calibration method of the present invention;

[0037] Figure 3 A grayscale image of a standard XE lamp measured by a spectrometer;

[0038] Figure 4 A spectral graph of a standard XE lamp image measured by a spectrometer;

[0039] Figure 5 This is a linear graph showing the relationship between spectral wavelength and pixel position.

[0040] Figure 6 Schematic diagram of the experimental setup for measuring methane sample gas;

[0041] Figure 7 This refers to the methane absorption cross section in the HITRAN database.

[0042] Figure 8 The graph shows the comparison curves of methane spectral absorption before wavelength correction, and the measured optical thickness (blue) and methane absorption cross section (red) after convolution sampling of the methane sample gas.

[0043] Figure 9 The image shows the wavelength-corrected methane spectral absorption curves, and the measured optical thickness (blue) and convolutional sampling cross-section (red) of the methane sample gas.

[0044] Figure 10 This is a schematic diagram of the principle of radiometric calibration of a spectrometer.

[0045] Figure 11 Measure the radiance of an integrating sphere with different numbers of lamps using a linear measuring instrument;

[0046] Figure 12 This is a schematic diagram of the radiation calibration factor α value;

[0047] Figure 13 This is a schematic diagram of the radiation calibration factor β value;

[0048] Figure 14 This is a graph verifying the results of radiation calibration and linearity measurement. Detailed Implementation

[0049] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0050] The technical solution of the present invention is a method for spectral calibration and radiometric calibration of a spectrometer, which will be described in detail below.

[0051] I. Spectral Calibration Methods

[0052] like Figure 1 The flowchart of the proposed spectral calibration method is shown below. The corresponding steps are:

[0053] (1) First, the uncalibrated spectrometer is calibrated using traditional spectral calibration (using a standard mercury lamp or argon lamp) to obtain a set of spectral calibration equations;

[0054] (2) Then, a sample gas measurement experiment was conducted on the spectrally calibrated spectrometer (any gas with an absorption peak within the wavelength range measured by the spectrometer). The sample gas experimental data were processed using differential absorption spectroscopy (DOAS). Based on the Lambert-Beer law, when light passes through the gas being measured, the absorption of light by the gas leads to light loss. The formula is as follows:

[0055]

[0056] In the formula, To output light intensity, For input light intensity, For the gas to be measured at wavelength Absorption cross section at the location, This represents the absorption path of the gas. This represents the concentration of the gas to be measured. This study improves upon the above formula, formalizing the fitting algorithm using the following formula:

[0057]

[0058] In the formula, and They are respectively filled into the sample gas pool The measurement spectrum of the gas to be measured. For the sample gas to be tested at wavelength Absorption cross section at the location, The slant column concentration (SCD) of the sample gas to be tested. This refers to the smoothing effect of all non-differential absorption, including Mie scattering, Rayleigh scattering, and broadband absorption, where the expression on the left side of the equation represents the optical differential thickness.

[0059] (3) At the same time, download the high-resolution absorption cross section data of the measured gas from the HITRAN database.

[0060] (4) Convolve and sample the optical differential thickness data in steps (2) and (3) with the high resolution of the gas to make the resolution of the two consistent. Then, use the peak finding algorithm to calculate the wavelength difference corresponding to the same gas absorption peak and use the difference to correct the spectral calibration equation.

[0061] (5) Finally, the revised spectral calibration equation is the final spectral calibration equation, thus completing the spectral calibration of the new method.

[0062] It is worth noting that, based on traditional spectral calibration, the spectral calibration utilizes high-precision, high-resolution gas absorption cross sections downloaded from the HITRAN database to complete the spectral calibration of the spectrometer, thereby improving the calibration accuracy.

[0063] II. Radiation Calibration Methods

[0064] like Figure 2 The diagram shows the flowchart for proposing a radiation calibration method. The corresponding steps are:

[0065] First, using the spectrometer after spectral calibration, the integrating sphere light source is measured at a fixed integration time (let's say X ms). The number of lamps turned on inside the integrating sphere is adjusted so that the integrating sphere emits light of different intensities, and the spectral response measured by the spectrometer is obtained at different intensities.

[0066] Meanwhile, the radiance data of the integrating sphere light source at different settings were measured using a linear measuring instrument.

[0067] At each wavelength, the spectrometer response data and the radiance data measured by the linear measuring instrument were linearly fitted for different intensities of integrating sphere light sources.

[0068] The slope α and intercept β of the linear fitting result are the radiometric calibration factors at the integration time X ms. In actual measurements, the integration time is first corrected, and then the radiometric calibration of the spectrometer is performed using the following formula:

[0069] L(λ) = (T / X) × α × N(λ) + β, where L(λ) is the radiance after calibration, N(λ) is the measured response value of the spectrometer, T is the integration time during actual measurement, and α and β are the radiometric calibration factors. Thus, the radiometric calibration of the spectrometer is completed.

[0070] The novel spectrometer calibration and radiometric calibration methods proposed above significantly improve the calibration accuracy of spectrometers and address the problems of poor stability and low accuracy caused by traditional spectral and radiometric calibration. Radiometric calibration: An integrating sphere is used as the light source, combined with a linear measuring instrument to complete the radiometric calibration of the spectrometer. Simultaneously, the linear response of the integration time is utilized to correct the radiometric calibration when measuring light sources of different intensities. Because the integrating sphere generates a spatially uniform light source through multiple internal reflections from its internal reflective coating, the new radiometric calibration exhibits higher stability and accuracy.

[0071] Example

[0072] In this example, a short-wave infrared spectrometer was used, and spectral and radiometric calibrations were performed on it. The specific spectrometer parameters are shown in the table below.

[0073]

[0074] As shown in the table above, the spectrometer's spectral range is 1595-1675 nm, so methane measurement is used to complete the spectral calibration. Below are application examples of spectral and radiometric calibration for a short-wave infrared spectrometer.

[0075] (1) Spectral calibration:

[0076] ① First, a marine optical xenon lamp (XE-2) was selected for traditional spectral calibration. The measurement results are as follows: Figure 3 and Figure 4 : Figure 3 This is a grayscale image of a standard xenon lamp (XE-2) measured by a spectrometer. Figure 4 This is a spectrum curve of a standard xenon lamp (XE-2) measured by a spectrometer. Spectral calibration is completed by determining the center positions of the two absorption peaks.

[0077] Then, a Gaussian function model was used to fit each peak, determining the position of the central peak and the spectral wavelength data set [X,Y] in the spectral response function. Since the spectrum is approximately linearly arranged on the detector, the least squares method was used to perform linear regression analysis on the data set and solve for the fitted equation and the fitted curve. Figure 5 ;

[0078] ② Secondly, a methane sample gas experiment was conducted on the spectrometer after preliminary spectral calibration. The experimental equipment combination is existing technology known to those skilled in the art. The overall experimental equipment consists of three parts: a short-wave infrared spectrometer, a sample gas cell, and an integrating sphere light source. During the experiment, the light emitted by the integrating sphere light source is received by the short-wave infrared spectrometer through the sample gas cell. The sample gas cell used is a cylindrical sealed tube with a length of 50 cm and a radius of 4.5 cm, with an inlet and an outlet at the top and bottom, respectively. Before the experiment, the sample gas cell is continuously flushed with N2 to avoid gas interference. When the sample gas cell is full, the background spectrum is measured. Then, the gas to be tested is continuously introduced into the sample gas cell at a rate of 6 L / min, and the measurement result is used as the measured spectrum. The principle diagram of the measurement using the integrating sphere as the system light source is shown below. Figure 6 Using the Differential Absorption Spectroscopy (DOAS) algorithm, the optical thickness data of the sample gas measurement is calculated as ln(I N2 / I CH4 ).

[0079] ③ Download high-resolution methane absorption cross-section data from the HITRAN database website; the image is as follows. Figure 7 ;

[0080] ④ Take the optical thickness data ln(I) from ② N2 / I CH4 The image is obtained by convolving and sampling the methane absorption cross section XS in ③ with the methane absorption cross section XS in ③, so that the resolutions of the two are consistent. Figure 8 As shown, it can be observed that the absorption peak of the methane sample gas measured by the calibrated spectrometer differs slightly from the standard methane absorption cross-section data. Therefore, for the same peaks in both, peak-finding processing is performed to find the center wavelength of the peaks, calculate the difference between the two, and revise the original spectral calibration equation.

[0081] ⑤ Calculations show that the difference between the above images is 0.03 nm. Therefore, the entire calibration spectrum needs to be shifted to the right by 0.03 nm, which is reflected in the equation by adding 0.03 nm. Thus, the corrected spectral calibration equation is:

[0082]

[0083] The corrected image is as follows Figure 9 As shown. The spectrometer calibration is now complete. The absolute wavelength error calibrated using this method is improved to 0.002 nm, which is nearly an order of magnitude higher than traditional spectroscopic calibration methods.

[0084] (2) Radiation calibration

[0085] Radiation calibration uses an integrating sphere as the light source. The intensity of the light source is adjusted by changing the number of lamps turned on within the integrating sphere. A linearity measuring instrument is used to measure the intensity of the light emitted by the integrating sphere. The specific measurement principle is as follows: Figure 10The experimental equipment combination is an existing technology known to those skilled in the art. The overall experimental equipment consists of four parts: a short-wave infrared spectrometer, a linear measuring instrument, a calibration gun, and an integrating sphere. The linear measuring instrument and the calibration gun are connected by optical fiber. During the experiment, the calibration gun of the linear measuring instrument and the light inlet of the spectrometer are placed adjacent to the inlet of the integrating sphere, so that the distance between the two from the inlet of the integrating sphere is the same, ensuring that the intensity of the integrated sphere light source received is the same. Then, the radiance output by the linear measuring instrument and the DN value measured by the imaging spectrometer are recorded in groups at different radiance levels.

[0086] ① Select the integration time of the shortwave infrared spectrometer as 100ms, and adjust the number of lamps turned on in the integrating sphere to one, two, three, and four lamps respectively, and measure the response value with the spectrometer respectively.

[0087] ② Measure the spectral radiance of the light source emitted by the integrating sphere for each lamp using a linearity measuring instrument, such as... Figure 11 ;

[0088] ③ At each wavelength, linear fitting is used to fit the spectral response and radiance data of spectrometers with one, two, and four lamps to obtain the radiation calibration factors α and β. Specifically, as shown below... Figure 12 and Figure 13 As shown;

[0089] ④ After obtaining the radiometric calibration factor, the data from three lamps were verified using an integrating sphere. Using the radiometric calibration formula, the result was calculated as: L(λ) = (T / X) × α × N(λ) + β; Figure 14 ;

[0090] ⑤ As can be seen from the above results, the radiometric calibration results are good and have good stability, with the radiometric calibration error decreasing from 0.966% to 0.165%.

[0091] The above describes the spectral and radiometric calibration methods proposed in this invention, applied to short-wave infrared imaging spectrometers. This method is also applicable to the ultraviolet band and linear spectrometers. The spectral and radiometric calibration methods proposed in this invention, by combining gas absorption cross-section data from the HITRAN database with traditional spectral calibration, and correcting the calibration equation through convolution sampling and peak-finding algorithms, improve the absolute wavelength error after spectral calibration from 0.022 nm to 0.002 nm, increasing accuracy by nearly an order of magnitude. Simultaneously, using an integrating sphere as the light source and combining it with a linear measuring instrument for radiometric calibration, and correcting the calibration factor through integration time, the radiometric calibration error is reduced from 0.966% to 0.165%, significantly improving the stability and accuracy of radiometric calibration. This effectively solves the problems of limited spectral lines, poor light source stability, and large extrapolation errors in traditional calibration methods, providing a solid guarantee for the high-precision application of spectrometers in environmental monitoring, materials science, remote sensing technology, and other fields.

[0092] The above specific embodiments are merely several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant teachings of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A method for spectral calibration and radiometric calibration of a spectrometer, characterized in that, Includes the following steps; Spectral calibration involves using a standard light source to perform initial spectral calibration on the uncalibrated spectrometer to obtain an initial spectral calibration equation. Then, optical differential thickness data is obtained through sample gas measurement experiments, and combined with standard gas absorption cross section data, the wavelength difference is calculated to correct the initial spectral calibration equation, resulting in the final spectral calibration equation. Radiometric calibration involves measuring the spectral response data of a variable intensity light source using a spectrometer that has undergone spectral calibration at a fixed integration time. This data is then combined with standard radiance measurement data for linear fitting to obtain the radiometric calibration factor. A linear measuring instrument is used to measure the radiance data of an integrating sphere light source at different lamp counts, which serves as the standard radiance measurement data. At each wavelength, the spectral response data corresponding to the same wavelength is linearly fitted with the standard radiance measurement data. The linear fitting employs the least squares method, and the fitting slope α and intercept β are determined through linear regression analysis. These slope α and intercept β are then used as the radiometric calibration factor at a fixed integration time of X ms. Then, the radiometric calibration factor is corrected according to the actual integration time, and the radiance after calibration is calculated by substituting it into the radiometric calibration formula. When the integration time T during actual measurement is inconsistent with the fixed integration time X ms, the slope α in the radiometric calibration factor is corrected by the proportional coefficient T / X. The corrected slope, intercept β and the actual measured response value N(λ) of the spectrometer are substituted into the radiometric calibration formula L(λ)=(T / X)×α×N(λ)+β to calculate the radiance after calibration L(λ).

2. The method for spectral calibration and radiometric calibration of a spectrometer according to claim 1, characterized in that, In the spectral calibration step, the initial spectral calibration of the uncalibrated spectrometer using a standard light source to obtain the initial spectral calibration equation is specifically as follows: a standard lamp is used as the standard light source, which can be any one of a mercury lamp, argon lamp, or xenon lamp. By measuring the spectral lines of the standard lamp, regression analysis is performed on the spectral line peaks and the detector pixel ordinal numbers to obtain the initial spectral calibration equation.

3. The method for spectral calibration and radiometric calibration of a spectrometer according to claim 1, characterized in that, The spectral calibration step, which involves obtaining optical differential thickness data through sample gas measurement experiments, specifically includes the following steps: A gas with an absorption peak within the measurement band of the spectrometer is selected as the sample gas, and the sample gas includes methane; Using a spectrometer that has undergone initial spectral calibration, the spectra of the sample gas cell were measured when nitrogen gas was introduced and when the sample gas was being tested. Differential absorption spectroscopy was used to process the measurement data, and the results were analyzed based on the Lambert-Beer law using the formula... Calculate optical differential thickness data; where, The measurement spectrum is for nitrogen filling. The measurement spectrum is obtained when the sample gas is filled. For the sample gas to be tested at wavelength The absorption cross section at that point The concentration of the sample gas in the inclined column is given. This refers to the smoothing effect of all non-differential absorptions, including Mie scattering, Rayleigh scattering, and broadband absorption.

4. The method for spectral calibration and radiometric calibration of a spectrometer according to claim 3, characterized in that, In the spectral calibration step, the specific method of combining standard gas absorption cross-section data is as follows: download the gas absorption cross-section data corresponding to the sample gas from the HITRAN database as the standard gas absorption cross-section data.

5. The method for spectral calibration and radiometric calibration of a spectrometer according to claim 1, characterized in that, The spectral calibration step, which calculates the wavelength difference to correct the initial spectral calibration equation, specifically includes the following steps: A. Perform convolution and sampling processing on the optical differential thickness data and the gas absorption cross section data to match the wavelength interval and number of data points between the two, ensuring consistent resolution; B. The processed data is analyzed using a peak-finding algorithm, which includes a Gaussian function fitting method. The center wavelength of the absorption peak is determined by performing Gaussian fitting on the absorption peak, and the wavelength difference corresponding to the absorption peaks of the same gas is calculated. C. Substitute the wavelength difference into the initial spectral calibration equation, correct the initial spectral calibration equation, and obtain the final spectral calibration equation.

6. The spectrometer spectral calibration and radiometric calibration method according to any one of claims 1-5, characterized in that, The spectrometer includes any one of short-wave infrared spectrometer, ultraviolet spectrometer, and linear spectrometer.

7. The method for spectral calibration and radiometric calibration of a spectrometer according to claim 6, characterized in that, When the spectrometer is a short-wave infrared spectrometer, its spectral range is 1595nm~1675nm, and the sample gas used in the spectral calibration step is methane.

8. The method for spectral calibration and radiometric calibration of a spectrometer according to claim 1, characterized in that, In the radiometric calibration step, the measurement of the spectral response data of a variable intensity light source using a spectrometer that has completed spectral calibration at a fixed integration time specifically includes: using an integrating sphere as a variable intensity light source, setting the fixed integration time of the spectrometer to X ms, changing the light source intensity by adjusting the number of lamps in the integrating sphere, wherein the adjustment of the number of lamps covers at least two different levels, including 1 lamp, 2 lamps, 3 lamps, and 4 lamps, and measuring the spectral response data of the spectrometer at different intensities respectively.

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