Method for correcting acquisition of so2 concentration image based on scaling coefficient and light dilution effect

Abstract

The application discloses a method for obtaining SO2 concentration image based on calibration coefficient and light dilution effect correction. The application comprises the following steps: collecting sky background and plume signal image by SO2 ultraviolet camera system, and calculating SO2 optical thickness; determining self-calibration coefficient by using sky background image, and converting optical thickness image into concentration image; and performing light dilution correction by combining distance and visibility information measured by distance measuring instrument and atmospheric visibility measuring instrument, so as to realize accurate inversion of SO2 concentration. Compared with the prior art, the application solves the defects that SO2 ultraviolet camera must rely on external equipment calibration and measurement error increases with the increase of detection distance. The application does not need additional calibration equipment, and self-calibration coefficient is combined with light dilution effect correction to obtain accurate SO2 concentration image. The application has the advantages of simple structure, convenient operation, high calibration precision and good real-time performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical remote sensing detection of polluted gas, and particularly relates to a method for correcting SO2 concentration image based on a calibration coefficient and light dilution effect. BACKGROUND

[0002] Atmospheric environmental pollution not only affects climate change, but also seriously threatens human life and health. The sources of polluted gas can be divided into natural and human emissions, such as volcanoes, industrial areas, power plants, etc. Among the many emission pollutants, one of the most serious pollutants is SO2. SO2 is a toxic gas emitted by human and natural sources. After being discharged into the atmosphere, it can form acid rain, acidify water, destroy soil, and cause adverse changes in the ecosystem. Therefore, studying and monitoring the emission of polluted gas helps to assess air quality and improve climate conditions. SO2 ultraviolet camera imaging detection technology has been rapidly developed due to its simplicity, high resolution, and other advantages, and is widely used in geological activity monitoring such as volcanic plume monitoring and volcanic eruption warning. With the improvement of the performance of filters and cameras, ultraviolet cameras are gradually used to measure SO2 pollution from human activity sources with lower concentrations. This technology can obtain two-dimensional images of plumes from pollution sources in real time, quickly and accurately. After image processing, it can directly reflect the SO2 concentration image at any position in the camera field of view. In actual operation, the SO2 ultraviolet camera does not directly obtain the SO2 concentration, but only measures the optical thickness of SO2 gas in the plume. It needs to use the calibration method to convert the measured SO2 optical thickness into SO2 concentration. The significance of calibration is to determine the calibration coefficient to achieve accurate inversion of SO2 concentration. However, the existing calibration methods all have the problem that the calibration accuracy is affected by the performance of external instruments, resulting in generally high systematic errors.

[0003] In fact, the accuracy of the calibration is not only affected by the instrument hardware parameters, but also by environmental factors such as monitoring distance and atmospheric visibility. During the atmospheric transmission of the sun scattered light, the sun scattered light interacts with gas molecules and aerosols in the atmosphere. After the sun light passes through the plume, some light is scattered between the instrument and the plume, which makes part of the light passing through the plume move out of the field of view of the camera, and the light outside the field of view moves into the field of view, forming interference light. With the increase of the distance between the instrument and the remote sensing target, the interference light replaces the light passing through the plume, which leads to the 'light dilution' effect of the plume signal. The weakening of the light dilution effect on the absorption signal is enhanced with the increase of the monitoring distance and the decrease of the atmospheric visibility. When monitoring the pollution source under the condition of long distance and low visibility, the calculated calibration coefficient k is much smaller than the true value, which leads to the underestimation of the actual SO2 concentration in the plume. The current calibration method cannot overcome the influence of the light dilution effect caused by the atmospheric ultraviolet scattering, and thus is not suitable for monitoring the long-distance pollution source; the DOAS method can obtain the calibration coefficient corrected by the light dilution effect in principle, but in actual operation, too many variables lead to too large statistical uncertainty of the measurement data, so that the light dilution effect cannot be effectively corrected. SUMMARY

[0004] To solve the above problems in the prior art, the purpose of the present application is to provide a method for obtaining an SO2 concentration image based on a calibration coefficient and a light dilution effect correction, which overcomes the problem of inaccurate SO2 concentration inversion caused by the influence of an external calibration device and the light dilution effect when SO2 ultraviolet camera is used to invert the SO2 concentration image.

[0005] To achieve the above purpose, the present application provides a method for obtaining an SO2 concentration image based on a calibration coefficient and a light dilution effect correction, which comprises the following steps:

[0006] Step S10: obtaining a real value of SO2 gas optical thickness of the plume by an SO2 ultraviolet camera

[0007] Step S20: determining a calibration coefficient, and converting the real value of the SO2 gas optical thickness into an SO2 concentration image

[0008] Step S30: correcting the SO2 concentration image by a light dilution effect, and obtaining an SO2 concentration image

[0009] In step S10, the following steps are included:

[0010] 1.1) imaging the sky background by the signal channel and the reference channel of the SO2 ultraviolet camera to obtain a signal channel sky background image I A0 and a reference channel sky background image I​​B0 ; the plume signal image I A and the plume signal image I B ,

[0011] 1.2) Calculate the optical thickness image τ A and the optical thickness image τ B ,

[0012] τ A = -ln(I A / I A0 ),

[0013] τ B = -ln(I B / I B0 ),

[0014] 1.3) Subtract the optical thickness image τ A from the optical thickness image τ B to obtain the optical thickness true value of the plume SO2 gas

[0015]

[0016] wherein, is the optical thickness true value of the SO2 gas;

[0017] wherein, the step S20 comprises:

[0018] 2.1) Define the function of the logarithm value R of the background intensity ratio of the signal channel and the reference channel with the change of the solar scattered spectrum L0(λ) as follows:

[0019]

[0020] wherein, λ is the wavelength, dλ is the integral of the wavelength,

[0021] Q(λ) is the quantum efficiency of the camera, T 310 (λ) is the transmittance of the 310 nm filter of the signal channel, T 330 (λ) is the transmittance of the 330 nm filter of the reference channel, the values of Q(λ), T 310 (λ) and T 330 (λ) are provided by the manufacturer of the SO2 ultraviolet camera and the ultraviolet filter,

[0022] 2.2) Define the SO2 optical thickness calculation value The relationship between the solar scattering spectrum L0(λ) and the solar scattering spectrum is as follows:

[0023]

[0024] in, This is the calculated value for the optical thickness of SO2.

[0025] The absorption cross section of SO2 gas was calculated using HITRAN2016 software.

[0026] This represents the column density of SO2 gas (i.e., the path integral of its concentration, expressed in ppm·m).

[0027] L0(λ) under different solar zenith angles can be calculated using atmospheric radiative transfer software such as MODTRAN.

[0028] 2.3) Due to the calculated value of SO2 optical thickness With solar scattering spectrum L0(λ) and SO2 gas column density The logarithm R of the ratio of background intensity in the signal channel and the reference channel is linearly correlated with the variable solar scattering spectrum L0(λ); therefore, the column density of SO2 gas can be determined by functional transformation. Optical thickness of SO2 gas The linear relationship between the logarithm R of the ratio of the background intensity of the signal channel and the reference channel is shown below:

[0029]

[0030] Then, the relationship function is determined by calculating the calibration curve between the logarithm R of the background intensity ratio of the signal channel and the reference channel and the calibration coefficient k, as shown below:

[0031] k = 1942.7·log R 0.84 ,

[0032] Furthermore, defining the optical thickness of SO2 With SO2 gas column density The functional relationship is as follows:

[0033]

[0034] 2.4) Based on the SO2 optical thickness defined in step 2.3) With SO2 gas column density Functional relationship The true optical thickness value of SO2 gas obtained in step S10 Convert to SO2 concentration image

[0035]

[0036] The step S30 comprises:

[0037] 3.1) Calculate the extinction coefficient ε(λ) of aerosol particles based on the atmospheric visibility V and the aerosol particle scattering coefficient q:

[0038]

[0039] Wherein,

[0040] q is the aerosol particle scattering coefficient, V is the atmospheric visibility, and the atmospheric visibility V is collected in real time by an atmospheric visibility measuring instrument,

[0041] 3.2) Obtain the monitoring distance d between the SO2 ultraviolet camera and the remote target based on the distance measuring instrument, and then calculate the correction coefficient C:

[0042] C = exp[-ε(λ)·d]

[0043] 3.3) The corrected SO2 concentration image is:

[0044]

[0045] It should be noted that the SO2 ultraviolet camera system comprises a pair of ultraviolet sensitive cameras with the same index and two ultraviolet bandpass filters with adjacent center wavelengths, and further comprises an atmospheric visibility measuring instrument and a distance measuring instrument. The ultraviolet camera A, the 310 nm filter, and the ultraviolet lens A are coaxially connected in sequence to form a signal channel. The ultraviolet camera B, the 330 nm filter, and the ultraviolet lens B are coaxially connected in sequence to form a reference channel.

[0046] The atmospheric visibility measuring instrument collects the atmospheric visibility of the day in real time.

[0047] The distance measuring instrument measures the monitoring distance between the SO2 ultraviolet camera and the remote target in real time.

[0048] Wherein, the signal channel and the reference channel image the sky background to obtain the sky background image of the signal channel and the sky background image of the reference channel respectively; the signal channel and the reference channel also image the pollution source plume to obtain the plume signal image of the signal channel and the plume signal image of the reference channel respectively.

[0049] The beneficial effects of the present application are:

[0050] Firstly, the present application is a method for self-calibration of SO2 ultraviolet camera without any auxiliary equipment or external device, which changes the problem that the traditional calibration precision is affected by the performance of external instruments, thereby greatly improving the calibration precision of SO2 ultraviolet camera.

[0051] Secondly, when monitoring the pollution source under long distance and low visibility conditions, the light attenuation effect will seriously interfere with the application of SO2 ultraviolet camera, leading to underestimation of SO2 concentration of smoke plume, and the existing traditional calibration method cannot effectively correct the influence of light attenuation effect on SO2 concentration inversion. However, the light attenuation correction method of the present application has the advantage of quantitative correction for different monitoring distances and atmospheric visibility, and can accurately obtain SO2 concentration information.

[0052] Thirdly, the present application is simple to operate: SO2 ultraviolet camera collects pollution source smoke plume image, atmospheric visibility measuring instrument collects atmospheric visibility, and distance measuring instrument collects monitoring distance. By virtue of the large field of view of SO2 ultraviolet camera, when applied to mobile pollution source monitoring, it is not necessary to frequently switch the system field of view to track the pollution source; the calibration precision is high: the filter is located behind the ultraviolet lens, which is less affected by the change of solar zenith angle, and the transmittance is known. In addition, the self-calibration method fully utilizes the camera measurement data, and can effectively improve the inversion precision in combination with light attenuation correction. Compared with the existing three calibration methods (standard bubble method, DOAS method and spectral calibration method), the self-calibration is not affected by external calibration equipment, and is more resistant to external environmental factors, so the calibration precision is higher; the real-time performance is good: the original image of pollution source smoke plume can be obtained in real time by SO2 ultraviolet camera, and the calibration coefficient can be determined in real time by combining with the self-calibration method, in addition, the monitoring distance and atmospheric visibility information can also be obtained in real time by using distance measuring instrument and atmospheric visibility measuring instrument, so that the light attenuation effect correction of the inversion result can be realized in real time. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 The flow chart of light attenuation effect correction and SO2 ultraviolet camera self-calibration method of the present application;

[0054] Figure 2 The sky background image of signal channel;

[0055] Figure 3 The sky background image of reference channel;

[0056] Figure 4 The smoke plume signal image of signal channel;

[0057] Figure 5 The smoke plume signal image of reference channel;

[0058] Figure 6This is an optical thickness image of the signal channel;

[0059] Figure 7 For reference channel optical thickness image;

[0060] Figure 8 This represents the true optical thickness of the SO2 gas.

[0061] Figure 9 The transmittance curves are for the 310nm filter in the signal channel and the 330nm filter in the reference channel.

[0062] Figure 10 The solar scattering spectrum was calculated using MODTRAN software.

[0063] Figure 11 This represents the relationship between the logarithm R of the background intensity ratio between the signal channel and the reference channel and the scaling factor k.

[0064] Figure 12 R is the logarithm of the ratio of the background intensity of the signal channel to that of the reference channel;

[0065] Figure 13 Image of SO2 concentration;

[0066] Figure 14 The curves showing the variation of the correction coefficient C with the monitoring distance d under different atmospheric visibility V;

[0067] Figure 15 This is an image of SO2 concentration after correction for photodilution effect;

[0068] Figure 16 A comparison of calibration curves obtained by the self-calibration method and the DOAS method. Detailed Implementation

[0069] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The method for obtaining SO2 concentration images based on calibration coefficients and photodilution effect correction according to the present invention will be further explained and illustrated below with reference to the accompanying drawings.

[0070] like Figure 1 As shown, the method for obtaining SO2 concentration images based on calibration coefficients and photodilution effect correction includes the following steps:

[0071] Step S10: Obtain the true value of the optical thickness of SO2 gas in the smoke plume using an SO2 ultraviolet camera.

[0072] Specifically, the SO2 ultraviolet camera uses atmospheric scattered light from the sun in the ultraviolet band as its light source, acquiring both sky background images and plume signal images. The optical thickness image is calculated using the ratio method combined with Beer-Lambert's law. Besides the absorption of SO2 gas in the plume, the Mie scattering process of particulate matter also produces an extinction effect. To eliminate the influence of particulate matter extinction on the SO2 gas measurement results, a dual-channel imaging method is used in actual measurements. This involves imaging the gas plume in two narrow bands at 310 nm and 330 nm, respectively, and then using the differential method to obtain the SO2 optical thickness image of the plume.

[0073] The SO2 ultraviolet camera system includes a pair of identical ultraviolet-sensitive cameras and two ultraviolet bandpass filters with adjacent center wavelengths. It also includes an atmospheric visibility meter and a distance measuring instrument. Ultraviolet camera A, a 310nm filter, and ultraviolet lens A are sequentially and coaxially connected to form a signal channel. Ultraviolet camera B, a 330nm filter, and ultraviolet lens B are sequentially and coaxially connected to form a reference channel. The atmospheric visibility meter can collect real-time atmospheric visibility data for the current day, and the distance measuring instrument can measure the real-time distance between the SO2 ultraviolet camera and the telemetry target.

[0074] First, the signal channel and reference channel of the SO2 ultraviolet camera image the sky background, respectively acquiring the sky background image I of the signal channel. A0 and reference channel sky background image I B0 The signal channel and reference channel also image the plume from the pollution source, acquiring plume signal images I in the signal channel respectively. A Plume signal image I from the reference channel B .

[0075] Then, the optical thickness image τ of the signal channel is calculated according to the Beer-Lambert law. A Optical thickness image τ of the reference channel B ,

[0076] Among them, the optical thickness image τ of the signal channel A The calculation method is as follows:

[0077] τ A =-ln(I A / I A0 )

[0078] Among them, the optical thickness image τ of the reference channel B The calculation method is as follows:

[0079] τ B =-ln(I B / I B0 )

[0080] Finally, the optical thickness images of the reference channel and the signal channel are subtracted by using the difference method to obtain the optical thickness real value of the plume SO2 gas

[0081]

[0082] Step S20, determining the scaling coefficient, converting the optical thickness real value of the SO2 gas into the SO2 concentration image

[0083] Specifically, there is a linear relationship between the SO2 concentration and the SO2 optical thickness Determine the scaling coefficient k, and the SO2 optical thickness image can be converted into the SO2 concentration image.

[0084] First, the following two formulas are used to calculate the logarithmic value R of the background intensity ratio of the signal channel and the reference channel and the SO2 optical thickness varying with the solar scattering spectrum

[0085]

[0086]

[0087] In the formula, is the absorption cross section of SO2 gas, is the SO2 concentration, i.e., the column density of SO2 gas, whose unit is ppm·m, Q(λ) is the quantum efficiency of the camera, T 310 (λ) is the transmittance of the 310 nm filter of the signal channel, T 330 (λ) is the transmittance of the 330 nm filter of the reference channel, and L0(λ) is the solar scattering spectrum. Among them, the quantum efficiency Q(λ) of the camera, the transmittance T 310 (λ) of the 310 nm filter, and the transmittance T 330 (λ) of the 330 nm filter are obtained according to the technical parameters provided by the ultraviolet camera and ultraviolet filter manufacturers, and the solar scattering spectrum L0(λ) under different solar zenith angles is calculated according to the MODTRAN atmospheric radiation transmission software, which is used in the subsequent self-scaling coefficient acquisition step.

[0088] The relationship between the logarithmic value R of the background intensity ratio of the signal channel and the reference channel and the scaling coefficient k can be obtained by function fitting, as shown in Figure 11 Since the function relationship between R and k is only determined by two system hardware indexes of the quantum efficiency of the camera and the transmittance of the ultraviolet filter, and only varies monotonously with the solar zenith angle, Figure 11 ​The relationship curve shown is universal.

[0089] The SO2 optical thickness is calculated from the measured value of the SO2 concentration and the solar scattered spectrum L0(λ) and the SO2 gas column density The logarithm of the ratio of the background intensity of the signal channel and the reference channel R is uniquely linearly related to the variable solar scattered spectrum L0(λ); therefore, the SO2 gas column density is determined by the conversion function The SO2 gas optical thickness and the linear relationship of the logarithm of the ratio of the background intensity of the signal channel and the reference channel R is as follows:

[0090]

[0091] Then, the relationship function is determined by calculating the calibration curve between the logarithm of the ratio of the background intensity of the signal channel and the reference channel R and the calibration coefficient k, as follows:

[0092] k = 1942.7 · log R 0.84 ,

[0093] Further, the function relationship of the SO2 optical thickness and the SO2 gas column density is defined The SO2 gas optical thickness true value obtained in step S10 is converted into an SO2 concentration image

[0094] In step S30, the SO2 concentration image is corrected for light dilution effect to obtain an SO2 concentration image

[0095] Specifically, in order to obtain the best field of view, the SO2 ultraviolet camera is placed several kilometers away from the plume. As the monitoring distance increases, more solar scattered light is scattered by atmospheric molecules (Mie and Rayleigh scattering) and aerosol particles, which causes the "dilution" of the plume signal. Within a few kilometers of measurement range, this effect can easily cause an underestimate of the actual SO2 concentration in the plume. By installing an atmospheric visibility measuring instrument and a distance measuring instrument on the SO2 ultraviolet camera system, the atmospheric visibility V on the day of remote sensing and the monitoring distance d are read respectively, and the correction coefficient C is calculated to correct the above SO2 concentration image for light dilution.

[0096] First, the atmospheric visibility V is determined by the real-time atmospheric visibility collected by the atmospheric visibility measuring instrument, and the aerosol particle scattering coefficient q is determined, which can be determined according to the following formula:

[0097] ​​

[0098] Subsequently, based on atmospheric visibility and the aerosol particle scattering coefficient q, the extinction coefficient ε(λ) of the aerosol particles was calculated:

[0099]

[0100] Finally, based on the extinction coefficient ε(λ) of the aerosol particles, and using the distance measuring instrument to obtain the monitoring distance d between the SO2 ultraviolet camera and the telemetry target, the correction coefficient C is calculated using the following formula:

[0101] C = exp[-ε(λ)·d]

[0102] Figure 3 The trend of the correction coefficient C with the monitoring distance is shown. For different atmospheric visibility V and monitoring distance d, the aerosol particle scattering coefficient q and extinction coefficient ε(λ) are determined to calculate the correction coefficient C.

[0103] Corrected SO2 concentration image for:

[0104]

[0105] Case Implementation and Verification Experiment Results

[0106] In step S10, the signal channel and reference channel of the SO2 ultraviolet camera image the sky background, respectively acquiring the sky background image I of the signal channel. A0 like Figure 2 As shown, reference channel sky background image I B0 like Figure 3 As shown; the signal channel and reference channel also image the pollution source plume, acquiring the plume signal image I of the signal channel respectively. A like Figure 4 As shown, the plume signal image I of the reference channel. B like Figure 5 As shown.

[0107] Based on the imaging principle of SO2 ultraviolet cameras, the optical thickness image τ of the signal channel is calculated. A like Figure 6 As shown; the calculated optical thickness image τ of the reference channel. B like Figure 7 As shown, the true optical thickness value of the SO2 gas plume is obtained by performing difference processing on the optical thickness images of the reference channel and the signal channel using the differential method. like Figure 8 As shown:

[0108] In step S20, the transmittance T of the 310nm filter in the signal channel of this case is... 310(λ) and the transmittance T of the 330nm filter for the reference channel 330 (λ) such as Figure 9 As shown. The solar scattering spectrum L0(λ) calculated using the MODTRAN atmospheric radiative transfer software is as follows: Figure 10 As shown. Through function fitting, the relationship between the logarithm R of the background intensity ratio of the signal channel and the reference channel and the scaling coefficient k can be obtained, as shown below. Figure 11 As shown. In this case, the logarithmic value R of the calculated ratio of the background intensity of the signal channel and the reference channel is as follows. Figure 12 As shown, its logarithm logR = 1.99, and the scaling coefficient k = 3440 is determined based on the relation. The obtained SO2 concentration image like Figure 13 As shown.

[0109] In step S30, the atmospheric visibility V = 30 km is collected in real time by an atmospheric visibility meter, and the aerosol particle scattering coefficient q = 1.3 is determined. Based on the atmospheric visibility and the aerosol particle scattering coefficient, the extinction coefficient ε(λ) = 0.27 of the aerosol particles is calculated. According to the extinction coefficient of the aerosol particles, and combined with the monitoring distance d = 2 km between the SO2 ultraviolet camera and the telemetry target obtained by the distance measuring instrument, the correction coefficient C = 0.57 is calculated. Figure 14 As shown. Corrected SO2 concentration image. like Figure 15 As shown.

[0110] To verify the accuracy of the method of this invention, its measurement data was compared with the data acquired by the spectrometer, and the calibration curves of the two methods were obtained as follows: Figure 16 As shown, the calibration results of the two methods have relatively good consistency, with an error of approximately 0.2%. All of the above demonstrates that the method provided by this invention can effectively complete the self-calibration task of the SO2 ultraviolet camera, possesses theoretical innovation, solves the problem of calibration accuracy being affected by the performance of external instruments, and can reasonably eliminate the influence of photodilution effect on SO2 concentration inversion, thereby improving the detection accuracy of the SO2 ultraviolet camera.

[0111] At the same time, through comparison Figure 13 and Figure 15It can be seen that the SO2 concentration after the light dilution correction is obviously higher than that before the correction. This is because when the SO2 ultraviolet camera remotely measures at a distance of 2 km from the target source, the sunlight scattered to the camera photosurface is affected by the light dilution effect, resulting in that part of the sunlight scattered through the smoke plume moves out of the camera field of view, and the sunlight scattered without the smoke plume information enters the field of view, finally causing the underestimation of the actual SO2 concentration in the smoke plume. The above all shows that the method provided by the present application can effectively complete the correction task of the SO2 concentration, thereby improving the inversion accuracy of the SO2 ultraviolet camera.

[0112] The above specific embodiments have shown and described the embodiments of the present application, but it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present patent, and the scope of the present patent is defined by the appended claims and their equivalents.

Claims

1. A method for obtaining SO2 concentration images based on calibration coefficients and photodilution effect correction, characterized in that... Includes the following steps: Step S10: Obtain the true value of the optical thickness of SO2 gas in the smoke plume using an SO2 ultraviolet camera. Step S20: Determine the calibration coefficients and obtain the true optical thickness value of SO2 gas. Convert to SO2 concentration image Step S30, analyze the SO2 concentration image. Correction for photodilution effect to obtain SO2 concentration image Step S10 includes: 1.1) Image the sky background using the signal channel and reference channel of the SO2 ultraviolet camera to obtain the sky background image I in the signal channel. A0 and reference channel sky background image I B0 The pollution source plume was imaged using the signal channel and reference channel of the SO2 ultraviolet camera, and plume signal images I of the signal channel were acquired respectively. A Plume signal image I from the reference channel B , 1.2) Calculate the optical thickness image τ of the signal channel according to Beer-Lambert's law. A Optical thickness image τ of the reference channel B , τ A =-ln(I A / I A0 ), τ B =-ln(I B / I B0 ), 1.3) Optical thickness image τ of the signal channel A Optical thickness image τ of the reference channel B Perform interpolation to obtain the true optical thickness of SO2 gas in the plume. in, This represents the true optical thickness of the SO2 gas. Step S20 includes: 2.1) Define the logarithmic relationship R between the ratio of background intensity of the signal channel and the reference channel as a function of the solar scattering spectrum L0(λ), as shown below: Where λ is the wavelength, and dλ is the integral over the wavelength. Q(λ) is the quantum efficiency of the camera. T 310 (λ) represents the transmittance of the filter in the signal channel. T 330 (λ) represents the filter transmittance of the reference channel. Q(λ), T 310 (λ) and T 330 The values ​​of (λ) were provided by the manufacturers of the SO2 ultraviolet camera and the ultraviolet filter, respectively. 2.2) Define the calculated value of SO2 optical thickness The relationship between the solar scattering spectrum L0(λ) and the solar scattering spectrum is as follows: in, This is the calculated value for the optical thickness of SO2. The absorption cross section of SO2 gas was calculated using HITRAN2016 software. The column density of SO2 gas. 2.3) Due to the calculated value of SO2 optical thickness With solar scattering spectrum L0(λ) and SO2 gas column density The logarithm R of the ratio of background intensity in the signal channel and the reference channel is linearly correlated with the variable solar scattering spectrum L0(λ); therefore, the column density of SO2 gas can be determined by functional transformation. Optical thickness of SO2 gas The linear relationship between the logarithm R of the ratio of the background intensity of the signal channel and the reference channel is shown below: Then, the relationship function is determined by calculating the calibration curve between the logarithm R of the background intensity ratio of the signal channel and the reference channel and the calibration coefficient k, as shown below: k=1942.7·log R 0.84 , Furthermore, defining the optical thickness of SO2 With SO2 gas column density The functional relationship is as follows: 2.4) Based on the SO2 optical thickness defined in step 2.3) With SO2 gas column density Functional relationship The true optical thickness value of SO2 gas obtained in step S10 Convert to SO2 concentration image in, Step S30 includes the following steps: 3.1) Calculate the extinction coefficient ε(λ) of aerosol particles based on atmospheric visibility V and aerosol particle scattering coefficient q: in, q represents the aerosol particle scattering coefficient, and V represents atmospheric visibility, which is collected in real time by an atmospheric visibility meter. 3.2) Based on the distance measuring instrument, obtain the monitoring distance d between the SO2 ultraviolet camera and the telemetry target, and then calculate the correction coefficient C: C = exp[-ε(λ)·d] 3.3) SO2 concentration image Correction for photodilution effect to obtain SO2 concentration image

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