Method for calculating spectral irradiance based on wide-bandwidth optical measurement data

Abstract

The invention relates to the technical field of optical radiation measurement, and discloses a method for calculating spectral irradiance based on wide-bandwidth optical measurement data, which comprises the following steps: firstly, correcting wide-bandwidth data into narrow-bandwidth data by adopting energy ratio correction, and obtaining the energy ratio by a standard light spectrum and actually measured optical filter transmittance without human intervention; 2, considering the difference of the spectral transmittance, normalizing the difference and multiplying the difference into a calibration coefficient, and correcting the influence caused by the difference of the transmittance of the optical filter; thirdly, polarization correction is carried out, extra transmissivity generated by polarization caused by film covering is corrected, an environment correction algorithm is incorporated, and errors generated due to film polarization influences are eliminated; in addition, radiation heating correction is carried out, a fitting curve is obtained according to the change of radiation deviation along with radiation intensity, and data are corrected. According to the invention, aiming at the condition that the optical filter is used for splitting light, the broadband optical measurement data is accurately corrected, the spectral irradiance calculation precision is improved, and a high-precision measurement effect on the basis of a low-cost structure is realized.

Description

Technical Field

[0001] The invention relates to the technical field of optical radiation measurement, and in particular to a method for calculating spectral irradiance based on wide-bandwidth optical measurement data. Background Art

[0002] Irradiance is an important optical parameter and is used in many optical fields. In the field of atmospheric science, irradiance is mainly used to describe the radiation intensity of natural light. Its unit is energy flux unit Wm -2 , and spectral irradiance (also called spectral irradiance) refers to the energy flux per unit wavelength, that is, the irradiance of a single spectrum, and the unit is mWm -2 nm -1 The spectral irradiance referred to in the present invention is the spectral irradiance conventionally defined in the art, which will not be described in detail below.

[0003] Natural light is directly or indirectly related to solar radiation, and can be roughly divided into direct light and scattered light. Direct light represents the radiation flux that reaches the instrument directly after being weakened by the atmosphere, and scattered light is the downward radiation flux caused by atmospheric molecules and suspended particles scattering sunlight. The scattering caused by gas molecules in the atmosphere is called Rayleigh scattering, and its downward radiation flux on a sunny day is reflected as the blue sky. The scattering caused by larger particles such as fog droplets and aerosols is described by Mie scattering. In addition to scattering, atmospheric matter also absorbs light, that is, atmospheric matter absorbs solar radiation energy and converts it into heat energy. Heat energy is then added to atmospheric energy transmission in other forms of energy. Atmospheric absorption is not reflected in irradiance, but in the attenuation of light in the atmosphere.

[0004] The instrument for measuring irradiance is a radiometer, which uses the photoelectric effect and energy conservation to obtain the signal of optical radiation intensity. The radiometer can measure multi-spectral or hyperspectral spectral irradiance data. The technology for measuring spectral irradiance is already very mature, and a variety of instruments can meet the needs of spectral irradiance measurement. The main difference in irradiance measurement technology lies in the spectroscopic method. General hyperspectral instruments need to use grating spectrometry, while instruments with few spectral bands can also use filter spectrometry.

[0005] The ideal narrow bandwidth optical signal is a bandpass transmission with rectangular characteristics, that is, it is a constant within the bandwidth ±Δλ (unit nm) and zero outside the bandwidth. Grating spectrometry can output rectangular signals, and although the filter is bandpass, the output signal is basically a peak signal, which is very different from the rectangular signal in terms of signal intensity and bandwidth. The most important thing is the bandwidth signal. Measuring spectral irradiance requires the collector to have a narrow spectral width to ensure high measurement accuracy. The instrument bandwidth of grating spectrometry can be ±3nm, while the bandwidth of filter spectrometry is much wider. Even if there are clear requirements for bandwidth, the peak structure of its output signal still leads to the input of out-of-domain signals and the widening of bandwidth. The wider the bandwidth of the filter, the greater the energy entering, and the higher the output voltage value. These deviations will be regarded as "signals" and are the main error sources of the instrument. Therefore, measuring irradiance with a wide bandwidth filter will result in large errors, which is one of the unresolved problems.

[0006] The Chinese patent with application number 201910302823.2 discloses a haze vertical structure detector, which is a miniature radiometer carried by a sounding balloon to detect the vertical profile of atmospheric irradiance and invert the distribution of substances in the atmosphere, forming a fog visibility profile detection system (FVP, Fog Visibility Profiler). The patent mentions that "spectral data is obtained by means of filters. The selection of spectra is divided into rough selection and fine selection. Rough selection is used to ensure effective coverage of the spectral range, with a balanced distribution in the range of 400-1000nm, and fine selection is used to avoid the main spectral absorption band. The optical sensor is located above the haze detector. There are multiple filters above the optical sensor. Each filter obtains data by a photoelectric tube. The number of photoelectric tubes is the same as the number of spectra. The data collected by the photoelectric panel is collected, amplified and output by the data amplifier circuit. The filter is covered with a cosine scatterer to achieve the effect of uniform light." This radiometer uses filters to provide bandpass data for each channel. Since the radiometer is a one-time instrument, it cannot use high-precision but expensive components. It can only use wide-bandwidth filters and hope to obtain the same measurement accuracy as narrow-bandwidth instruments. However, the data obtained by the wide-bandwidth collector is difficult to accurately give the spectral irradiance value, and sometimes the error can reach more than 1 times the actual value. Therefore, how to improve the spectral irradiance measurement accuracy of the wide-bandwidth collector using filter splitting has become an urgent problem to be solved. Summary of the invention

[0007] The purpose of the present invention is to provide a method for calculating spectral irradiance based on wide-bandwidth optical measurement data, to accurately correct the wide-bandwidth optical measurement data for an irradiance meter using filter spectroscopy, to improve the calculation accuracy of spectral irradiance, and to achieve high-precision measurement effects based on a low-cost structure.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] A method for calculating spectral irradiance based on wide bandwidth optical measurement data, the method comprising the following steps:

[0010] (1) Energy ratio correction: Determine the energy ratio σ based on the standard lamp spectrum and the measured filter transmittance sd (λ n ), the energy ratio σ sd (λ n ) represents the proportion of energy in each spectral band, and the formula is expressed as:

[0011]

[0012] In the formula, E max is the maximum irradiance of the standard lamp in the visible spectrum, E sd (λ) is the irradiance of the standard lamp, γ(λ) is the measured transmittance of each spectral band of the filter, λ is the wavelength variable, and λ n represents the nth specific central wavelength, Δλ is the half bandwidth;

[0013] (2) Transmittance calibration: Using Trios as a standard instrument, calibrate the transmittance of each spectral band and perform normalization. The transmittance of each spectral band is normalized to η(λ n ), where the transmittance of each spectral band is corrected and the formula is expressed as:

[0014]

[0015] In the formula, when Trios is at a set distance from the standard lamp, the measured irradiance is E γ0 (λ), on this basis, add the filter, cosine scatterer and coating, and the measured irradiance is E(λ), γ film (λ) is the transmittance caused by the coating, γ cos (λ) is the transmittance caused by the cosine scatterer, γ filt (λ) is the transmittance caused by the filter;

[0016] (3) Polarization correction: According to the refractive index and transmittance of each spectral band of the coating material, the transmittance T(λ) caused by polarization is obtained. n ), and the transmittance is corrected point by point. Considering both direct light and scattered light, let T(λ n ) after correction consists of two parts, expressed as:

[0017]

[0018] Where, T max (λ n) is the maximum transmittance caused by polarization; f0(λ n ) represents the influence of scattered light on irradiance; f1(λ n ) is the effect of direct light on irradiance, f0(λ n ) and f1(λ n ) are the constraints between

[0019] f0(λ n )+f1(λ n )=1 (15)

[0020] (4) Calculation of spectral irradiance: Based on energy ratio σ sd (λ) and transmittance η(λ n ) Improved calibration coefficient S(λ n ), the improved S(λ n ) and κ(λ n ) into the following formula to calculate the spectral irradiance, that is, the input energy E(λ n ), the formula is:

[0021]

[0022] Improved S(λ n ) is used for static calibration of the instrument, κ(λ n ) is related to the solar zenith angle and belongs to environmental correction;

[0023] Among them, the improved calibration coefficient is:

[0024]

[0025] In the formula, the output voltage corresponding to the nth spectrum segment is v(λ n ), the output voltage v generated by the dark current of the instrument is measured when the incident radiation is zero dark (λ n ).

[0026] Furthermore, it also includes:

[0027] (5) Radiation heating correction: Considering the error caused by solar radiation heating the instrument shell, the spectral irradiance is calculated, that is, the input energy of the nth spectral band is E(λ n ) is expressed as:

[0028]

[0029] Among them, the measured spectral irradiance affected by radiation heating is E0(λ n ), fitting coefficient a(λ n ), b(λ n ) and c(λ n ) are all functions of temperature.

[0030] Furthermore, in the radiation heating correction process of step (5), the derivation process of formula (20) is as follows:

[0031] Assume that the measured spectral irradiance affected by radiation heating is E0(λ n ), the irradiance change caused by temperature is ΔE0(λ n ), then the irradiance caused by the radiation intensity alone is E(λ n )for:

[0032] E(λ n )=E0(λ n )-ΔE0(λ n ) (17)

[0033] According to ΔE0(λ n ) with ΔE0(λ n )’s changing curve, and its quadratic fitting is:

[0034] ΔE0(λ n )=a(λ n )+b(λ n )E(λ n )+c(λ n )E 2 (λ n ) (18)

[0035] Among them, E(λ n ) is the value provided by the comparative instrument Trios; each spectrum segment has a different response to temperature, a(λ n ), b(λ n ), c(λ n ) is related to the spectrum and is obtained by fitting the measured data;

[0036] Substituting (18) into (17), we obtain

[0037] E(λ n )=E0(λ n )-[a(λ n )+b(λ n )E(λ n )+c(λ n )E 2 (λ n )] (19)

[0038] Wherein, formula (20) is obtained based on formula (19).

[0039] Furthermore, in step (3), the polarized transmittance T(λ n ) is a function related to wavelength and is expressed as:

[0040]

[0041] Where i1 and i2 are the angle of incidence and angle of refraction, respectively, which are determined by the law of sines:

[0042] n1sini1=n2sini2 (10)

[0043] Where n1 is the refractive index of the atmosphere and n2 is the refractive index of the coating.

[0044] Furthermore, in step (4), based on the energy ratio σ sd (λ) and transmittance η(λ n ) Improved calibration coefficient S(λ n ), including:

[0045] Based on the energy ratio and transmittance, the wide bandwidth voltage data is corrected for bandwidth and transmittance, and the narrow bandwidth voltage data is obtained as follows:

[0046] v sd (λ n )-v dark (λ n )=[V sd (λ n )-v dark (λ n )]σ sd (λ n )η(λ n ) (6)

[0047] In the formula, v sd (λ n ) is the narrow bandwidth output voltage when measuring standard lamps, V sd (λ n ) is the wide bandwidth output voltage when using filter spectrometry measurement, and formula (6) establishes the conversion relationship between the narrow bandwidth output voltage and the wide bandwidth output voltage;

[0048] The calibration coefficient S(λ before improvement n ) is calculated as:

[0049]

[0050] In the formula, E sd (λ n ) is the irradiance of a standard lamp;

[0051] Substitute formula (6) into the calibration coefficient S(λ n ) is calculated in formula (3), and the improved calibration coefficient is obtained:

[0052]

[0053] The improved calibration coefficients in formula (8) increase the energy ratio and transmittance and are used to convert wide bandwidth data into narrow bandwidth data.

[0054] Furthermore, in step (4), the derivation process of formula (16) is as follows:

[0055] Let λ represent the wavelength variable, and λ n represents the central wavelength of the nth spectral band, Δλ is the half bandwidth, the ideal narrow bandwidth optical signal is a rectangular wave, which is constant within the bandwidth ±Δλ and zero outside the bandwidth. Let the measured input energy of the nth spectral band be E(λ n ), the output voltage is v(λ n ), the relationship between the two is described by a linear function:

[0056] E(λ n )=p(λ n )v(λ n )+q(λ n ) (1)

[0057] Among them, p(λ n ) and q(λ n ) are the slope and intercept of the linear fit. When the incident radiation is zero, the output voltage v generated by the dark current of the instrument is measured. dark (λ n ), (1) becomes:

[0058]

[0059] Since the transmittance caused by polarization is related to the incident angle and is an environmental parameter, it cannot be given in the calibration coefficient. The transmittance can only be corrected point by point, that is,

[0060]

[0061] T(λ n ) is corrected to κ(λ n ), the corrected S(λ n ) and κ(λ n ) into (13), we can get formula (16).

[0062] According to a specific embodiment provided by the present invention, the method for calculating spectral irradiance based on wide-bandwidth optical measurement data provided by the present invention discloses the following technical effects:

[0063] When developing a micro-irradiance meter that uses filters for spectroscopy, the irradiance error obtained is large due to the wide bandwidth of the filter. From an optical point of view, it is a difficult problem to invert the real physical quantity using the measurement results of wide bandwidth. The present invention proposes a bandwidth correction algorithm, which realizes the accurate inversion of irradiance by correcting multiple parameters. First, the energy ratio method is used for correction to correct the wide bandwidth data to narrow bandwidth data. The energy ratio is obtained by the standard lamp spectrum and the measured filter transmittance without human intervention; second, considering the difference in spectral transmittance, it is normalized and multiplied by the calibration coefficient to correct the influence caused by the difference in filter transmittance; the third step is called polarization correction, which corrects the additional transmittance caused by the polarization caused by the coating, and incorporates it into the environmental correction algorithm to eliminate the error caused by the polarization of the film; in addition, radiation heating correction can also be performed, and the fitting curve is obtained according to the change of radiation deviation with radiation intensity to correct the data. The results show that high-precision irradiance data can be obtained by the method described in the present invention. Standardization tests show that after these corrections, the results are highly consistent with the standard instrument, achieving a good measurement effect, indicating that these correction steps constitute a reliable bandwidth correction algorithm. Therefore, the present invention accurately corrects the wide-bandwidth optical measurement data, improves the calculation accuracy of the spectral irradiance, and achieves a high-precision measurement effect based on a low-cost structure, which is more practical and suitable for practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0065] Figure 1 This is a cross-sectional view of the components of the optical signal acquisition system of a multi-spectral instrument with filter spectroscopy according to an embodiment of the present invention, wherein ① is a coating, ② is a cosine scatterer, ③ is a filter, ④ is an optical sealing ring, ⑤ is a photoelectric tube, ⑥ is a data acquisition circuit board, Figure 2 All components in the are circular;

[0066] Figure 2 Schematic diagram of optical signals transmitted through the filter according to an embodiment of the present invention, wherein (a) is the transmittance of five spectral bands measured, (b) is the spectral distribution of the transmittance of the 535nm filter, the green solid line is the transmission spectrum curve of the filter, the black solid line is the position of the center spectrum, and the pink shadow indicates the range of the set bandwidth;

[0067] Figure 3Schematic diagram of the change of film transmittance with the solar altitude angle;

[0068] Figure 4 This is a schematic diagram of the selection results of f1 determined empirically;

[0069] Figure 5 is the error of irradiance inversion under strong radiation conditions;

[0070] Figure 6 For cloudless weather on July 3, 2024, the changes in radiation deviation with radiation intensity and their fitting curves for five spectral bands with wavelengths of 427nm, 474nm, 535nm, 606nm, and 671nm;

[0071] Figure 7 Schematic diagram of the role played by various correction means;

[0072] Figure 8 This is a comparison chart of the FVP instrument (red line) and the standard instrument Trios (black line) in the Qingdao Baguanshan standardized test. The left column is the comparison chart of July 3, July 4, and July 5 corresponding to the wavelength of 427nm; the right column is the comparison chart of July 3, July 4, and July 5 corresponding to the wavelength of 606nm;

[0073] Fig. 9 This is a comparison chart of the synchronous observation results of the FVP instrument and the standard instrument Trios in the Qingdao Baguanshan standardization test. The left picture is a comparison chart of the results at a wavelength of 427nm, and the right picture is a comparison chart of the results at a wavelength of 606nm;

[0074] Fig.10 The numbers in the figure are the station numbers of each station;

[0075] Fig.11 Schematic diagram for the comparison between FVP inversion results and Trios synchronous observation results;

[0076] Fig.12 Schematic diagram of the method for calculating spectral irradiance based on wide-bandwidth optical measurement data in an embodiment of the present invention. DETAILED DESCRIPTION

[0077] 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.

[0078] The purpose of the present invention is to provide a method for calculating spectral irradiance based on wide-bandwidth optical measurement data, so as to obtain accurate irradiance measurement results when developing a micro-irradiance meter using a filter for light splitting.

[0079] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0080] The measurement principle of the micro-radiometer is to use the photoelectric effect in physics, use a photoelectric tube as the data acquisition unit, and place an optical filter in front. The incident radiation energy is received by the acquisition unit, which changes the current of the photoelectric tube, and the output voltage generated is used as the output signal of the micro-radiometer. The optical signal acquisition system of the micro-radiometer is as follows: Figure 1 As shown: the system includes a filter ③, which is used to obtain light in a specific wavelength range; a cosine scatterer ②, also known as a Lambertian body, which converts light from all directions into cosine scattered light; a coating ① plays a fixing role and can adjust the transmittance; a phototube ⑤ and a circuit board ⑥ carrying the phototube are used to collect optical signals; the entire optical signal collection system is optically sealed through a sealing ring ④. The optical signal collection system with filters as the main body has the characteristics of a wide bandwidth, and the error of using it to obtain irradiance data is large. The following will study how to effectively correct the data to meet the needs of high-precision irradiance measurement.

[0081] like Fig.12 As shown, the method for calculating spectral irradiance based on wide-bandwidth optical measurement data provided by the present invention comprises the following steps:

[0082] (1) Energy ratio correction: Determine the energy ratio σ based on the standard lamp spectrum and the measured filter transmittance sd (λ);

[0083] (2) Transmittance correction: Use Trios as a standard instrument to calibrate the transmittance of each spectral band and perform normalization;

[0084] (3) Polarization correction: According to the refractive index and transmittance of each spectral band of the coating material, the transmittance T(λ) caused by polarization is obtained. n ), and the transmittance is corrected point by point. In which, the direct light and scattered light are comprehensively considered to correct T(λ n ) is κ(λ n );

[0085] (4) Calculation of spectral irradiance: Based on energy ratio σ sd (λ) and transmittance η(λ n ) Improved calibration coefficient S(λ n ), the improved S(λ n ) and κ(λ n) into the following formula to calculate the spectral irradiance, that is, the input energy E(λ n ), the formula is:

[0086]

[0087] Among them, the improved calibration coefficient is:

[0088]

[0089] In the formula, the output voltage corresponding to the nth spectrum segment is v(λ n ), the output voltage v generated by the dark current of the instrument is measured when the incident radiation is zero dark (λ n );

[0090] (5) Radiation heating correction: Considering the error caused by solar radiation heating the instrument shell, the spectral irradiance is calculated, that is, the input energy of the nth spectral band is E(λ n ) is expressed as:

[0091]

[0092] Among them, the measured spectral irradiance affected by radiation heating is E0(λ n ), fitting coefficient a(λ n ), b(λ n ) and c(λ n ) are all functions of temperature.

[0093] Example:

[0094] The present invention is directed to Figure 1 The embodiment of the optical signal acquisition system of the micro-radiometer shown in the figure provides a method for calculating spectral irradiance based on wide-bandwidth optical measurement data, and the specific steps are as follows:

[0095] (1) Standard calibration method for irradiance measuring instruments

[0096] For the sake of clarity, the wavelength variable is λ, and n represents the central wavelength of the nth spectral band, and Δλ is the half bandwidth. The ideal narrow-bandwidth optical signal is a rectangular wave, which is constant within the bandwidth ±Δλ (in nm) and zero outside the bandwidth. Assume that the measured input energy of the nth spectral band is E(λ n )(Unit is mWm -2 nm -1 ), the output voltage is v(λ n )(unit is V), the relationship between the two is described by a linear function:

[0097] E(λ n )=p(λn )v(λ n )+q(λ n ) (1)

[0098] Among them, p(λ n ) and q(λ n ) are the slope and intercept of the linear fit. When the incident radiation is zero, the output voltage v generated by the dark current of the instrument can be measured. dark (λ n ), (1) becomes

[0099]

[0100] Among them, S(λ n ) is the calibration coefficient, which needs to be obtained through optical calibration. In a dark room, the instrument is directly measured with a standard lamp to obtain

[0101]

[0102] In the formula, E sd (λ n ) is the irradiance of the standard lamp, v sd (λ n ) is the output voltage when measuring the standard lamp. n ) is determined, the accurate spectral irradiance value can be calculated using formula (2).

[0103] However, formula (2) requires that the narrow bandwidth requirement be met, that is, the narrower the half-bandwidth Δλ, the better. For example, the bandwidth of the optical instrument Trios, which uses the grating spectrometer principle, is 3nm, and accurate irradiance values ​​can be obtained using formula (2). If the bandwidth is very large, the method obtained by formula (2) cannot be used directly, because the measured output voltage contains the energy obtained within a larger bandwidth range, and the irradiance obtained is also the average value of a larger range, which cannot reflect the correct spectral irradiance. Therefore, obtaining irradiance using wide-bandwidth data is a difficult problem in optical measurement.

[0104] Our research shows that the problem that needs to be solved in order to obtain accurate irradiance using wide-bandwidth data is to accurately understand the optical characteristics of the instrument and the signal, and to correct the wide-bandwidth output voltage signal and convert it into an accurate irradiance value.

[0105] (2) Filter bandwidth and transmittance

[0106] The optical signal passing through the filter is very different from the rectangular peak and presents a peak-like structure, such as Figure 2 As shown in (a).

[0107] like Figure 2As shown in (b), taking the transmission spectrum characteristics of the 535nm spectral filter as an example, the transmittance distribution of the transmission spectrum is given. The measured voltage V sd (λ n ) actually reflects the result of integrating the radiation energy entering the entire spectral range. The pink shaded area is the range of ±10nm, and the signal within this range is the signal we need to measure. As can be seen from the figure, outside the set bandwidth, some light can still pass through the filter and enter the sensor. Therefore, it is necessary to obtain the voltage data V from the wide bandwidth sd (λ n ) to accurately extract narrow bandwidth voltage data, v sd (λ n ) and v(λ n ) can be used to calculate the irradiance using equations (2) and (3).

[0108] Considering that the irradiance of the standard lamp represents the energy of the radiation and is a known energy flux, the proportion of energy in each spectral band can be calculated σ sd (λ),

[0109]

[0110] In the formula, E max is the maximum irradiance of the standard lamp in the visible spectrum. Equation (4) is equivalent to the weighted average and normalization of the radiation energy of each spectrum. The weight function γ(λ) is the variation of transmittance with wavelength. Take Δλ = 10nm to calculate the σ of each spectrum. sd (λ n ). The red light of the standard lamp is very strong, and the energy obtained within the set bandwidth is close to 80%, while the energy obtained by the purple light in the same bandwidth is only 17%. sd (λ n ) satisfies the measurement of natural light and needs to ensure that the calculation result of formula (4) is as accurate as possible.

[0111] A careful study of formula (4) shows that σ sd In fact, it reflects the distribution characteristics of the standard lamp spectrum, that is, the change of spectral irradiance with wavelength, which is basically the average value of the spectrum of the standard lamp within the set bandwidth. The actual transmittance needs to be considered to reflect the proportion of this energy actually entering the instrument. The spectral characteristics reflecting the transmittance are represented by the spectral transmittance γ(λ n ) expression. Ideally, the transmittance of each spectral band should be the same; however, due to the inevitable deviation in the filter processing process, the actual transmittance of each spectral band is not consistent. For example, the transmittance of 427nm is significantly lower than that of other spectral bands. Figure 2 (a). Therefore, it is necessary to use the actual transmittance for correction. The transmittance of each spectral band is normalized to

[0112]

[0113] In the formula, γ max is the maximum value of transmittance in all spectral bands.

[0114] The wide bandwidth voltage data is subjected to bandwidth correction and transmittance correction, and the narrow bandwidth voltage data is obtained as follows:

[0115] v sd (λ n )-v dark (λ n )=[V sd (λ n )-v dark (λ n )]σ sd (λ n )η(λ n ) (6)

[0116] (3) Determination of spectral transmittance

[0117] According to formula (4), we can accurately calculate σ sd (λ n ) is based on the knowledge of the spectral distribution γ(λ) of the transmittance. A hyperspectral instrument is required to measure the spectral distribution. Here, Trios is used as the standard instrument. When Trios is 50 cm away from the standard lamp, the measured irradiance is E γ0 (λ). On this basis, add the filter, cosine scatterer and fixed film, and the received irradiance is E(λ). The overall spectral transmittance of the system is:

[0118]

[0119] In the formula, γ film (λ) is the transmittance caused by the film, γ cos (λ) is the transmittance caused by the cosine scatterer, γ filt (λ) is the transmittance caused by the filter. Note that to measure E(λ), the filter, cosine scatterer and fixed film must be placed close to the trios lens without reducing the measuring distance and must be light-tight. If a light-proof lens is used, the measuring distance is changed and the algorithm for obtaining γ(λ) is much more complicated.

[0120] like Figure 2 As shown in (a), each filter does not produce an ideal rectangular transmittance, but a peak transmittance centered on the central spectrum that decreases to both sides, and there is also a certain degree of asymmetry. Therefore, no matter what the nominal spectrum width of the filter is, the voltage data needs to be corrected to obtain the irradiance.

[0121] (4) Determination of calibration coefficient

[0122] Substituting (6) into (3), we obtain:

[0123]

[0124] The physical meaning of formula (8) is to obtain the energy in a narrow bandwidth by adjusting the calibration coefficient, thereby giving an accurate irradiance value.

[0125] We expect that we can obtain accurate irradiance by using formula (8) as the calibration coefficient. However, actual results show that this method works well only when the sunlight is nearly vertically incident, and when the sunlight is obliquely incident, deviations will occur, sometimes large deviations.

[0126] (5) Effect of thin film on transmittance

[0127] Since there is a film on the surface of the instrument to fix the cosine scatterer and the filter, it is this film that changes the light energy entering the instrument, causing signal problems. Studies have shown that it is the film that changes the solar radiation flux entering the instrument, which leads to deviations in the measurement results at oblique incidence. In fact, the film can be removed to eliminate this problem, but because the film has the function of improving the transmittance of light, the film is retained.

[0128] The coating is an optical medium that will reflect and transmit on its upper and lower interfaces. It affects light in three ways: (a) weakening the transmitted light; (b) frequency shift of the spectrum; and (c) change in the transmittance of oblique incident light. Among them, equation (7) already includes the effect of the film on the transmittance; there is still an air layer between the film and the cosine scatterer, so the effect of the frequency shift can be ignored. What needs to be solved is the effect of the film on oblique incident light.

[0129] The reflection and refraction of light at the film interface will produce polarized light. According to the optical polarization theory, the transmittance of polarization is a function related to the wavelength.

[0130]

[0131] Where i1 and i2 are the angle of incidence and angle of refraction, respectively, which are determined by the law of sines:

[0132] n1 sini1=n2sini2 (10)

[0133] Where n1 is the refractive index of the atmosphere, and n2 is the refractive index of the film. According to the refractive index measurement standard, the nominal refractive index of the material is the refractive index of sodium yellow light. For oblique incidence, different light has different refractive indices, so dispersion occurs. The actual refractive index of each wavelength is different, which may be higher or lower than the nominal refractive index. Generally speaking, the longer the wavelength, the smaller the refractive index. The relationship between refractive index and wavelength is

[0134]

[0135] Assuming that the wavelength λ0 of sodium yellow light is 589.3nm and the nominal refractive index n0 of the medium is 1.73, then

[0136]

[0137] That is, the refractive index is inversely proportional to the wavelength. The results obtained using formula (12) are shown in Table 1. It can be seen from the table that the actual refractive index of short waves is higher than the nominal refractive index, and the actual refractive index of long waves is lower than the nominal refractive index.

[0138] Table 1 Relationship between transmittance and refractive index of thin films

[0139]

[0140] The transmittance calculated using formula (11) is Figure 3 As shown in the figure, when the incident angle is within 40°, the difference is very small, but after 40°, the transmitted radiation decreases significantly. When the incident angle is greater than the Brewster angle (approximately equal to 62.2°), the transmittance of light decreases rapidly. This is why a large error occurs at oblique incidence.

[0141] The difference in refractive index caused by polarization leads to a difference in transmittance. Taking light with an incident angle of 46° as an example, the transmittance of long waves is the largest, and the transmittance of short waves is reduced. Under oblique incidence conditions, the film weakens the transmitted light, causing the instrument to receive less energy than it actually does. It is necessary to divide the transmittance when calculating the irradiance to offset the effect of the film. Since the transmittance is related to the angle of incidence and is an environmental parameter, it cannot be given in the calibration coefficient. The transmittance can only be corrected point by point, that is,

[0142]

[0143] The physical meaning of this correction is that the voltage signal actually received is weakened by the film, which will cause the inverted irradiance to be lower than the actual value. n ) represents the proportion of the weakened light signal, so the voltage signal will be corrected to obtain accurate irradiance.

[0144] However, there is a problem with formula (13). It is very accurate when the solar zenith angle is small, but when the solar zenith angle is close to the horizontal, the error increases rapidly and even distortion occurs. We analyzed the reasons for the problem as follows: The transmittance given by formula (13) is only suitable for direct light. In the case of heavy fog and no direct light at all, the instrument will still receive scattered light from the fog. Therefore, in the inversion algorithm, not only direct light but also scattered light needs to be considered.

[0145] In order to reflect this feature, let T(λ n ) consists of two parts,

[0146]

[0147] Among them, T max (λ n ) is the maximum transmittance; f0(λ n ) represents the influence of scattered light on irradiance; f1 is the influence of direct light, and the constraint between f0 and f1 is,

[0148] f0(λ n )+f1(λ n )=1, (15)

[0149] That is, f0 and f1 only need to determine one value. When the apex angle is the smallest, the transmittance is the largest, κ(λ n ) is equal to the maximum transmittance T max (λ n ), which has a good correction effect. When the apex angle is large, the transmittance is small, κ(λ n ) is equivalent to the influence of scattered light, tending to f0(λ n )T max (λ n ).

[0150] In fact, there is no available theory or mature experience for the selection of f0 and f1. We can only determine it empirically, that is, after inverting all comparative data, determine the f1 with the smallest variance as the calibration coefficient. Figure 4 It shows that the minimum relative deviation occurs when f0:f1 is equal to 0.5:0.5. The physical meaning of the ratio of scattered light to direct light given by formula (14) is that although the ratio of direct light to scattered light is constantly changing, a ratio can be selected for the entire observation process, at which the relative deviation of irradiance inversion is the smallest.

[0151] Therefore, when the zenith angle is known during measurement, equation (15) can be adjusted to:

[0152]

[0153] Improved S(λ n ) is used for static calibration of the instrument, κ(λ n ) is related to the solar zenith angle and is an environmental correction.

[0154] This result shows that for data obtained with wide-bandwidth filters, the standard calibration process can only obtain the irradiance of vertically incident sunlight; once the sunlight is incident at an angle, further correction is required to eliminate the additional effects of polarization caused by the film.

[0155] (6) Errors under strong radiation conditions

[0156] After the above corrections, the data obtained are in good agreement with the results of Trios. When the temperature is not very high, without considering the error caused by the radiation intensity, the energy ratio correction, transmittance correction, and polarization correction can be used to achieve accurate measurement. However, when the radiation is strong, the error is still large ( Figure 5 The blue curve) requires further radiation heating correction. Our research shows that the error in this case of strong radiation is caused by the heating of the instrument shell by solar radiation. The shell of the plastic instrument absorbs solar radiation energy under the sun, and the increase in the shell temperature will produce additional thermal radiation, which will affect the measurement results. There are two ways to weaken the influence of solar radiation: one is to coat the instrument with reflective material to weaken the solar energy entering the instrument; the other is to add a metal heat transfer layer to the outer surface to transfer the heat as quickly as possible so that it cannot enter the instrument. This method cannot be used because the reflected light generated by the reflective material will affect the scattered light intensity of particulate matter in the overlying atmosphere, causing signal drift or noise. Adding a metal shell to the instrument is an effective way. Some precision optical instruments use metal shells. However, the thick metal shell is heavy and not suitable for profile detection; and the thin metal shell cannot completely eliminate radiation heating.

[0157] We studied the effect of radiation heating and found that if the instrument casing is not made of reflective or highly thermally conductive materials and is allowed to be heated by solar radiation, the temperature of the instrument will rise rapidly, but will not rise any further after reaching an equilibrium temperature. Figure 6 The data from July 3, 2024, is used to show the change of radiation deviation with radiation intensity under cloudless weather conditions. It can be clearly seen from the figure that under direct sunlight, the radiation deviation of each spectral band is closely related to the radiation intensity, which gives us a hint that the error caused by instrument heating can be corrected by its relationship with radiation intensity.

[0158] Assume that the measured spectral irradiance affected by radiation heating is E0(λ n ), the irradiance change caused by temperature is ΔE0(λ n ), then the irradiance caused by the radiation intensity alone is E(λ n ),

[0159] E(λ n )=E0(λ n )-ΔE0(λn ) (17)

[0160] According to ΔE0(λ n ) with E0(λ n )’s changing curve, and its quadratic fitting is:

[0161] ΔE0(λ n )=a(λ n )+b(λ n )E(λ n )+c(λ n )E 2 (λ n ) (18)

[0162] Among them, E(λ n ) is the value provided by the comparative instrument Trios. Each spectrum segment responds differently to temperature, so a(λ n ), b(λ n ), c(λ n ) is related to the spectrum and needs to be fitted from the measured data. The fitting result is as follows Figure 6 As shown by the red line, it can obviously well reflect the deviation caused by radiation heating.

[0163] Substituting equation (18) into equation (17), we obtain:

[0164] E(λ n )=E0(λ n )-[a(λ n )+b(λ n )E(λ n )+c(λ n )E 2 (λ n )] (19)

[0165] In the formula, E(λ n ) is the actual observed value, and the solution is

[0166]

[0167] Equation (20) is the final correction result, which effectively eliminates the influence of radiation ( Figure 5 red line).

[0168] It should be pointed out that the effect of solar radiation on irradiance is not only related to the radiation intensity, but also to the temperature. According to the laws of thermodynamics, there is a balance between radiation heating and heat conduction on the instrument surface. Therefore, the fitting coefficient a(λ n ), b(λ n ) and c(λ n ) are all functions of temperature.

[0169] Although the instrument temperature will change under the conditions of solar radiation heating and outside temperature, these correction coefficients are still essentially related to the instrument structure, depending on the material, thickness, and response of the instrument shell to heating. Through field tests under various weather conditions, fitting coefficients related to the instrument material can be obtained to achieve correction for instrument radiation heating.

[0170] (7) The role of various corrections

[0171] The present invention proposes various correction algorithms to solve the problem of obtaining accurate irradiance from wide bandwidth sensors. Here, taking the 34th observation station of Qianliyan Island as an example, the various correction methods play the role of Figure 7 The measurement time of station 34 is April 28, 2024, at 8:01 in the morning, with a solar zenith angle of 57.35°. Dense fog appeared during the observation period, which is very representative of its correction.

[0172] exist Figure 7 In the figure, the curve “standard” is the correction result obtained by standard calibration according to formula (3), which shows that the wide bandwidth data is quite different from the results of the comparison instrument, and the shorter the wavelength, the greater the difference in irradiance. The curve “standard+band” is the curve with bandwidth correction σ added. sd As a result, the wide bandwidth data is converted into narrow bandwidth data, and the result is substantially improved, but the error in the short-wave part is still large. The curve "standard+band+trans" adds the transmittance correction, as shown in formula (8), which greatly improves the transmittance of the spectrum band with low transmittance. The curve "Total" means "standard+band+trans+film", which adds the film correction on the basis of the existing correction, which reflects the additional effect of polarization on transmittance. Figure 7 It represents the observation at 8 a.m., when the temperature was low and the radiation intensity was also low, so no radiation heating correction was needed.

[0173] After these corrections, the results are highly consistent with those of the standard comparison instrument, and the inverted irradiance is very close to that of the standard instrument, achieving the ideal measurement effect and becoming a reliable algorithm.

[0174] (8) Verification of bandwidth correction algorithm

[0175] In order to prove the reliability of the algorithm, standardized tests were carried out in the field. Under natural conditions, for different weather conditions and different solar zenith angles, the FVP instrument using the method of the present invention was bundled with a newly calibrated standard instrument for synchronous observation to determine the accuracy of the inverted irradiance.

[0176] The verification test was conducted at the Baguanshan Meteorological Observatory of Ocean University of China from July 3 to 5, 2024. July 3 was clear and the next two days were cloudy. In order to test the adaptability of the algorithm to various solar zenith angles, the test was conducted from noon to 18:00 every day, and the measurement results that met the minimum zenith angle and the maximum zenith angle were given. Since the observation time of the FVP instrument is less than 1 hour, the instrument needs to be restarted after the observation, and the observation is made more than 5 times a day, with each interruption of about 10 minutes.

[0177] The irradiance of the spectrum on July 3 is greater than 100mWm -2 nm -1 The fitting coefficient a(λ n ), b(λ n ) and c(λ n ) is used to calibrate all test results. The results are as follows Figure 8 As shown, due to space limitations, Figure 8 Only the results of 427nm and 606nm are given, and the results of other spectral bands are also close. As can be seen from the figure, the inversion results are highly consistent with the results of the standard instrument, whether it is the overall change trend or the details of the changes caused by the cloud layer. This result shows that the bandwidth correction algorithm proposed in the present invention meets the needs of data correction in terms of accuracy.

[0178] Comparison chart of FVP and Trios Fig. 9 It can be seen that no matter whether it is strong radiation or weak radiation, the irradiance obtained is highly consistent with the observation results of Trios, achieving satisfactory results.

[0179] (9) Application examples of bandwidth correction algorithm

[0180] We conducted a sea fog observation at Qianliyan Island Ocean Station in April 2024. A total of 38 balloons were released, and three dense fog profiles were successfully observed. Several atmospheric profiles without fog were also observed, and Trios observations were carried out at the same time. FVP uses a bandwidth correction algorithm to calculate irradiance. Some time before the balloon release, the results of FVP measurements can be compared with the observations of Trios, and the inversion algorithm of spectral irradiance can be applied to experiments.

[0181] Under field conditions, it is not possible to use true values ​​for verification, so only comparative tests can be performed. Field experiments are different from standardized tests and have some uncertainties: (1) Due to the narrow terrain and sunlight conditions on the island, the placement of Trios is not completely consistent with that of FVP, which affects the comparability of the two. (2) Due to the obvious spatial differences in irradiance in dense fog, the deviation is likely to represent the actual situation and not necessarily a problem with the instrument algorithm. (3) During the comparative test, Trios was placed under unobstructed conditions, while the FVP instrument was hung with balloons, which had a certain impact on the reception of direct light.

[0182] The FVP measurement results are very close to the Trios simultaneous measurement results. The RMS deviation of the 5 spectrum segments is 67mW m - 2 nm -1 , the absolute deviation is only 4.24mW m -2 nm -1 , which is a relatively ideal result.

[0183] A total of 38 sets of data were obtained from the Qianliyan observations. The relative deviations of the remaining Trios data are as follows: Fig.10 As shown. It can be seen from the figure that there are 4 stations with large relative errors: 2, 11, 29, and 30. Station 2 was at 5 a.m., and the solar altitude angle was too low. The position of FVP at station 11 is low, at the upper edge of the fog, while the position of Trios is higher, and the two are not comparable. The inversion result of station 29 is actually very good, but there is a problem with the photoelectric tube in the 4th spectrum segment, and the irradiance obtained is very low. Station 30 is the only station measuring in the rain, and due to the lack of necessary research and experiments on the impact of rain on irradiance, its inversion result is lower than that of Trios. Excluding the data of the above 4 stations, data of 34 stations are available. Excluding these 4 stations, the relative deviations of the remaining stations can be seen. Fig.10 It can be seen that the average relative deviation of all stations is less than 15%, among which, the average relative deviation of the inversion of 28 stations is less than 10%, which meets the practical requirements.

[0184] The results of the comparison between irradiance and trios are as follows Fig.11 As shown in the figure, it can be seen that in foggy conditions, the irradiance is generally lower than 800mW m -2 nm -1 , all the values ​​are near the diagonal line, indicating that the algorithm of the present invention can give accurate inversion results. In the case of large irradiance, it is fog-free weather, direct light is dominant, and the relative deviation is below 0.18, but the inversion results of stations 37 and 19 have large deviations, which is related to the position difference of the two instruments.

[0185] When developing a micro-irradiance meter that uses filters for spectroscopy, we hope to obtain accurate irradiance measurement results. However, since the bandwidth of the filter is wide and it presents a peak-shaped light-transmitting structure, the acquired data contains energy in a large wavelength range and cannot accurately invert the irradiance. From an optical point of view, it is a difficult problem to invert the real physical quantity using the measurement results of wide bandwidth. The present invention proposes a bandwidth correction algorithm, which realizes the accurate inversion of irradiance through four steps of correction.

[0186] The first step of correction is called energy ratio correction. First, the energy ratio method is used to introduce σ sd (λ n ), correcting the wide bandwidth data. sd (λ n The physical meaning of ) is the proportion of the received light energy within the bandwidth ±Δλ. Through this coefficient, the data of the wide spectrum is successfully converted into the measurement results of the narrow spectrum. sd (λ n ) is to eliminate the significant difference between the standard lamp spectrum and the solar spectrum, and establish the applicability of the calibration coefficient to the solar spectrum. sd (λ n ) reflects the mutual influence between the standard lamp spectrum and the filter transmittance, thus establishing a common measurement system for light and filters. This relationship has been proven to be applicable under various natural light conditions, without considering the difference in light under foggy and non-fog conditions. sd (λ n ) is unique in that it is entirely obtained from the standard lamp spectrum and the measured filter transmittance without any human intervention.

[0187] The second step of correction is called transmittance correction. The filter transmittance γ(λ n ) is mainly caused by the coating thickness control process in the production process. Since the coating materials of different wavelengths are different, it is difficult to achieve the same transmittance. n ) is normalized and multiplied into the calibration coefficient, which actually corrects the influence caused by the difference in filter transmittance and makes the measurement results of each spectral band more comparable.

[0188] The third step of correction is called polarization correction. The instrument coating polarizes the reflected and transmitted light, generating polarized light. When the incident angle is large, the transmittance of light passing through the film will change, causing significant errors, and additional corrections are required to obtain accurate irradiance. This patent application proposes to obtain the transmittance caused by polarization based on the refractive index and transmittance of each spectral band of the film material, and incorporate it into the correction algorithm, eliminating the errors caused by the polarization effect of the film.

[0189] The fourth step is called radiation heating correction. When the solar radiation is very strong, it will directly heat the shell of the instrument, causing the temperature of the instrument shell to rise. Since the photoelectric tube that receives the light signal will receive additional energy due to the increase in the temperature of the instrument, it will cause measurement errors. Our research shows that the radiation heating of the instrument shell has two characteristics: first, the instrument shell is very thin and the temperature rises quickly; second, the instrument will quickly reach the equilibrium temperature. These two characteristics allow us to obtain a fitting curve based on the change of radiation deviation with radiation intensity and correct the data. The results show that this correction method can obtain high-precision irradiance data.

[0190] After these corrections, the results are highly consistent with the standard instrument. From July 3 to 5, 2024, we conducted a standardized test on the effectiveness of the above algorithm at the Qingdao Baguanshan Meteorological Observatory. The results showed that the irradiance obtained was highly consistent with the data of the standard instrument, regardless of whether there was fog or no fog, achieving the ideal measurement effect, indicating that these correction steps constitute a reliable bandwidth correction algorithm.

[0191] We conducted a sea fog observation at Qianliyan Island Ocean Station in April 2024, launching a total of 38 balloons. Before the balloons were launched, the data of FVP could be compared with the standard instrument Trios, and the inversion algorithm of spectral irradiance was applied to the experiment. The results showed that the data obtained by the calculation method provided by the present invention had good consistency with the comparison instrument.

[0192] Therefore, research has shown that the wide-bandwidth data obtained using filters has a large deviation. The algorithm provided by the present invention effectively corrects the wide-bandwidth data and obtains accurate irradiance inversion results.

[0193] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method for calculating spectral irradiance based on wide-bandwidth optical measurement data as described above is implemented.

[0194] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0195] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for general technicians in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope.

[0196] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for calculating spectral irradiance based on wide bandwidth optical measurement data, applied to a radiometer using filter spectroscopy, characterized in that: The following steps are involved: (1) Energy ratio correction: Determine the energy ratio σ based on the standard lamp spectrum and the measured filter transmittance sd (λ n ), the energy ratio σ sd (λ n ) represents the proportion of energy in each spectral band, and the formula is expressed as: In the formula, E max is the maximum irradiance of the standard lamp in the visible spectrum, E sd (λ) is the irradiance of the standard lamp, γ(λ) is the measured transmittance of each spectral band of the filter, λ is the wavelength variable, and λ n represents the nth specific central wavelength, Δλ is the half bandwidth; (2) Transmittance calibration: Using Trios as a standard instrument, calibrate the transmittance of each spectral band and perform normalization. The transmittance of each spectral band is normalized to η(λ n ), where the transmittance of each spectral band is corrected and the formula is expressed as: In the formula, when Trios is at a set distance from the standard lamp, the measured irradiance is E γ0 (λ), on this basis, add the filter, cosine scatterer and coating, and the measured irradiance is E(λ), γ film (λ) is the transmittance caused by the coating, γ cos (λ) is the transmittance caused by the cosine scatterer, γ filt (λ) is the transmittance caused by the filter; (3) Polarization correction: According to the refractive index and transmittance of each spectral band of the coating material, the transmittance T(λ) caused by polarization is obtained. n ), and the transmittance is corrected point by point. Considering both direct light and scattered light, let T(λ n ) after correction consists of two parts, expressed as: Where, T max (λ n ) is the maximum transmittance caused by polarization; f0(λ n ) represents the influence of scattered light on irradiance; f1(λ n ) is the effect of direct light on irradiance, f0(λ n ) and f1(λ n ) are: f0(λ n )+f1(λ n )=1 (15) (4) Calculation of spectral irradiance: Based on energy ratio σ sd (λ) and transmittance η(λ n ) Improved calibration coefficient S(λ n ), the improved S(λ n ) and κ(λ n ) into the following formula to calculate the spectral irradiance, that is, the input energy E(λ n ), the formula is: Among them, the improved calibration coefficient is: In the formula, the output voltage corresponding to the nth spectrum segment is v(λ n ), the output voltage v generated by the dark current of the instrument is measured when the incident radiation is zero dark (λ n ).

2. The method for calculating spectral irradiance based on wide-bandwidth optical measurement data according to claim 1, characterized in that: Also includes: (5) Radiation heating correction: Considering the error caused by solar radiation heating the instrument shell, the spectral irradiance is calculated, that is, the input energy of the nth spectral band is E(λ n ) is expressed as: Among them, the measured spectral irradiance affected by radiation heating is E0(λ n ), fitting coefficient a(λ n ), b(λ n ) and c(λ n ) are all functions of temperature.

3. The method for calculating spectral irradiance based on wide-bandwidth optical measurement data according to claim 2, characterized in that: In the radiation heating correction process of step (5), the derivation process of formula (20) is as follows: Assume that the measured spectral irradiance affected by radiation heating is E0(λ n ), the irradiance change caused by temperature is ΔE0(λ n ), then the irradiance caused by the radiation intensity alone is E(λ n )for: E(λ n )=E0(λ n )-ΔE0(λ n ) (17) According to ΔE0(λ n ) with ΔE0(λ n )’s changing curve, and its quadratic fitting is: ΔE0(λ n )=a(λ n )+b(λ n )E(λ n )+c(λ n )E 2 (l n ) (18) Among them, E(λ n ) is the value provided by the comparative instrument Trios; each spectrum segment has a different response to temperature, a(λ n ), b(λ n ), c(λ n ) is related to the spectrum and is obtained by fitting the measured data; Substituting (18) into (17), we obtain E(λ n )=E0(λ n )-[a(λ n )+b(λ n )E(λ n )+c(λ n )E 2 (l n )] (19) Wherein, formula (20) is obtained based on formula (19).

4. The method for calculating spectral irradiance based on wide-bandwidth optical measurement data according to claim 1, characterized in that: In the step (3), the polarized transmittance T(λ n ) is a function related to wavelength and is expressed as: Where i1 and i2 are the angle of incidence and angle of refraction, respectively, which are determined by the law of sines: n1sini1=n2sini2 (10) Where n1 is the refractive index of the atmosphere and n2 is the refractive index of the coating.

5. The method for calculating spectral irradiance based on wide-bandwidth optical measurement data according to claim 1, characterized in that: In step (4), based on the energy ratio σ sd (λ) and transmittance η(λ n ) Improved calibration coefficient S(λ n ), including: Based on the energy ratio and transmittance, the wide bandwidth voltage data is corrected for bandwidth and transmittance, and the narrow bandwidth voltage data is obtained as follows: v sd (l n )-v dark (l n )=[V sd (l n )-v dark (l n )]s sd (l n )η(λ n ) (6) In the formula, v sd (λ n ) is the narrow bandwidth output voltage when measuring standard lamps, V sd (λ n ) is the wide bandwidth output voltage when using filter spectrometry measurement, and formula (6) establishes the conversion relationship between the narrow bandwidth output voltage and the wide bandwidth output voltage; The calibration coefficient S(λ before improvement n ) is calculated as: In the formula, E sd (λ n ) is the irradiance of a standard lamp; Substitute formula (6) into the calibration coefficient S(λ n ) is calculated in formula (3), and the improved calibration coefficient is obtained: The improved calibration coefficients in formula (8) increase the energy ratio and transmittance and are used to convert wide bandwidth data into narrow bandwidth data.

6. The method for calculating spectral irradiance based on wide-bandwidth optical measurement data according to claim 1, characterized in that: In step (4), the derivation process of formula (16) is as follows: Let λ represent the wavelength variable, and λ n represents the central wavelength of the nth spectral band, Δλ is the half bandwidth, the ideal narrow bandwidth optical signal is a rectangular wave, which is constant within the bandwidth ±Δλ and zero outside the bandwidth. Let the measured input energy of the nth spectral band be E(λ n ), the output voltage is v(λ n ), the relationship between the two is described by a linear function: E(λ n )=p(λ n )v(λ n )+q(λ n ) (1) Among them, p(λ n ) and q(λ n ) are the slope and intercept of the linear fit. When the incident radiation is zero, the output voltage v generated by the dark current of the instrument is measured. dark (λ n ), (1) becomes: Since the transmittance caused by polarization is related to the incident angle and is an environmental parameter, it cannot be given in the calibration coefficient. The transmittance can only be corrected point by point, that is, T(λ n ) is corrected to κ(λ n ), the corrected S(λ n ) and κ(λ n ) into (13), we can get formula (16).

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