Method for selecting minimum test distance of target infrared radiation characteristics

Abstract

The present invention relates to a method for selecting a minimum test distance of target infrared radiation characteristics, comprising the following steps: determining the highest calibration temperature of a surface source black body when a spectroradiometer fills the field of view for calibration, calculating the radiation emittance of the surface source black body at the highest calibration temperature, calculating the radiation flux function of the surface source black body at the highest calibration temperature, calculating the radiation emittance of the target, calculating the radiation flux function of the target, determining the relationship between the area ratio of the target within the full field of view and the radiation emittance ratio, determining the preliminary minimum test distance of the target infrared radiation characteristics, and determining the minimum test distance of the target infrared radiation characteristics. The present invention determines the minimum test distance of the target infrared radiation characteristics based on a method for comparing the saturation of the radiation flux response voltage value on the detector image plane after the black body and the target radiation brightness pass through an optical system; the minimum test distance of the target infrared radiation characteristics determined by the method is verified, and the relative error is 1%.

Description

Technical Field

[0001] The invention belongs to the technical field of infrared radiation characteristic testing of high-temperature targets, and in particular relates to a method for selecting a minimum testing distance between a spectrum detection device and an infrared target. Background Art

[0002] In the target infrared radiation characteristics test, when testing the infrared radiation characteristics of a target within a known temperature range, the key is to determine the distance between the target and the spectrum detection device in order to obtain accurate target radiation characteristics.

[0003] At present, before testing the infrared radiation characteristics of the target, a black body is used as a standard radiation source, and the radiation power and voltage response curves are calibrated using a linear calibration method that fills the field of view. When the infrared radiation characteristics of the high-temperature target are tested using the calibrated radiation power and voltage response curves, when the detection distance is short, the detector voltage response will be saturated, and the infrared radiation characteristics of the target cannot be truly obtained; when the detection distance is far, since the target accounts for a small proportion in the detector field of view, the background proportion will increase, the atmospheric absorption effect will increase, and the signal-to-noise ratio will be small. In both cases, accurate target radiation characteristics cannot be obtained, and the method of frequently moving the spectral detection equipment to obtain the test distance will greatly reduce the test efficiency; therefore, how to efficiently determine the minimum distance between the spectral detection equipment and the target still requires a clear method. Summary of the invention

[0004] In order to overcome the shortcomings of low efficiency and low selection accuracy in determining the minimum test distance of target infrared radiation characteristics, the present invention proposes a method for selecting the minimum test distance of target infrared radiation characteristics.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] A method for selecting a minimum test distance for target infrared radiation characteristics comprises the following steps:

[0007] Step 1: Determine the highest calibration temperature of the surface source blackbody when the spectroradiometer fills the field of view.

[0008] The spectroradiometer is used as the test equipment and the surface blackbody is used as the standard radiation source to calibrate the spectroradiometer to fill the field of view. When the voltage saturation of the indium telluride channel of the spectroradiometer reaches the upper limit, the surface blackbody temperature is the highest calibration temperature T1 of the surface blackbody when the spectroradiometer is calibrated to fill the field of view.

[0009] Step 2: Calculate the radiation emittance of the surface source blackbody at the highest calibration temperature

[0010] The radiation emittance M1 of the surface source blackbody at the highest calibration temperature T1 is:

[0011]

[0012] In formula (2), c1 is the first radiation constant, c1 = 3.7418 × 10 8 m / s, c2 is the second radiation constant, c2=1.4388×10 -16 W·m 2 , λ is the wavelength of the measurement band, λ1 is the lower limit of the wavelength of the measurement band, and λ2 is the upper limit of the wavelength of the measurement band.

[0013] Step 3: Calculate the radiation flux function of the surface source blackbody at the highest calibration temperature

[0014] According to the propagation law of light flux in the optical imaging system, the radiation flux function of the standard radiation source projected onto the spectroradiometer detector through the optical system is:

[0015] P=βτLΩA (3)

[0016] In formula (3), P is the radiation flux projected onto the spectroradiometer detector through the optical system, β is the atmospheric transmittance, τ is the transmittance of the internal optical system of the spectroradiometer, L is the target spectral radiation brightness, Ω is the aperture angle of the internal optical system of the spectroradiometer, and A is the detector area of ​​the spectroradiometer.

[0017] When the surface source blackbody is at the highest calibration temperature, the radiation flux function of the surface source blackbody on the spectroradiometer detector is:

[0018] P1=β1τL1ΩA (4)

[0019] In formula (4), P1 is the radiation flux of the surface source black body projected onto the detector at the highest calibration temperature, that is, the radiation flux of the surface source black body at the highest calibration temperature; β1 is the atmospheric transmittance between the spectroradiometer and the surface source black body. Under ideal conditions, β1=1; L1 is the radiation brightness of the surface source black body at the highest calibration temperature.

[0020] According to the radiation characteristics of the radiation source, the radiation brightness of the surface source black body at the highest calibration temperature is related to the radiation emittance, and the relationship is as follows:

[0021]

[0022] Substituting equation (5) into equation (4), we can obtain the radiation flux function of the surface source blackbody at the highest calibration temperature, as shown below.

[0023]

[0024] At this point, the radiation flux function of the surface source blackbody at the highest calibration temperature is obtained.

[0025] Step 4: Calculate the target's radiant emittance

[0026] Taking any radiation source as the target and the spectroradiometer as the test equipment, the radiation emittance M2 of the target is related to the temperature T2 and the wavelength of the target, and the radiation emittance M2 of the target can be calculated by the following formula.

[0027]

[0028] In formula (7), T2 is the target temperature.

[0029] Step 5: Calculate the radiation flux function of the target

[0030] When selecting the minimum test distance for the target's infrared radiation characteristics, the influence of atmospheric attenuation on radiation is not considered for the time being. The radiation flux function of the target at a certain distance reflected on the detector of the spectroradiometer is calculated. Since the target does not fill the field of view at a certain distance, the projection of the target on the detector of the spectroradiometer is also not full. When the area of ​​the target in the full field of view is γ, the area of ​​the target is A1, the full field of view area of ​​the spectroradiometer at a certain distance is A2, and the area of ​​the target projected onto the detector of the spectroradiometer is A b According to the symmetric relationship of the triangle ratio, the area ratio γ of the target in the whole field of view is proportional to the area A projected onto the detector of the spectroradiometer. b , the detector area A of the spectroradiometer; the relationship between the target area ratio γ in the full field of view and the target area A1 and the full field of view area A2 of the spectroradiometer at a certain distance is as follows:

[0031]

[0032]

[0033] According to the radiation characteristics of the radiation source, the radiation brightness of the target is related to the radiation emittance, and the relationship is as follows:

[0034]

[0035] According to the propagation law of light flux in the optical imaging system, when the target is at a certain distance during the spectroradiometer test, the radiation flux function projected onto the spectroradiometer detector through the optical system is:

[0036] P2=β2τL2ΩA b (11)

[0037] In formula (11), P2 is the radiation flux on the spectroradiometer detector when the target is at a certain distance, that is, the radiation flux of the target, and L2 is the radiation brightness of the target. The influence of atmospheric attenuation on radiation is not considered for the time being, that is, in the ideal state, β2 = 1.

[0038] By combining equations (8), (10) and (11), we can get the radiation flux function of the target as follows:

[0039]

[0040] Step 6: Determine the relationship between the target area ratio γ in the full field of view and the radiation emittance ratio

[0041] When the spectroradiometer is calibrated with full field of view, the voltage saturation of the spectroradiometer reaches the upper limit at the highest calibration temperature of the surface source black body. In order to make the calibration data of the spectroradiometer valid, the following conditions need to be met: the radiation flux P2 of the target is less than or equal to the radiation flux P1 of the surface source black body at the highest calibration temperature. That is:

[0042] p2≤p1 (13)

[0043] Combining equation (6), equation (12) and equation (13), we get the following equation:

[0044]

[0045] Formula (14) is the relationship between the target area ratio γ in the whole field of view and the radiation emittance ratio.

[0046] Step 7: Determine the initial minimum test distance of the target infrared radiation characteristics

[0047] According to the relationship between the target area ratio γ in the full field of view and the radiation emittance ratio, the initial minimum test distance R of the target infrared radiation characteristics is determined. min .

[0048] Step 8: Determine the minimum test distance of the target infrared radiation characteristics

[0049] When actually measuring the infrared radiation characteristics of a target, that is, under non-ideal conditions, the influence of atmospheric transmittance should be considered.

[0050] The initial minimum test distance of the target infrared radiation characteristics obtained in step 7 is calculated by taking into account the influence of atmospheric transmittance. min The atmospheric radiation transmission characteristics calculation software MODTRAN is used to generate the atmospheric transmittance β3 at the preliminary minimum test distance.

[0051] According to the propagation law of light flux in the optical imaging system, when the target is at a certain distance and the influence of atmospheric transmittance is considered during the spectroradiometer test, the radiation flux function projected onto the spectroradiometer detector through the optical system is:

[0052] P3=β3τL2ΩA b (18)

[0053] In formula (18), P3 is the radiation flux on the detector when the target is at a certain distance considering the atmospheric transmittance, and β3 is the atmospheric transmittance between the spectroradiometer and the target.

[0054] By combining equation (8), equation (10) and equation (18), we can get the following equation:

[0055]

[0056] Formula (19) is the radiation flux function when the target is at a certain distance.

[0057] When the spectroradiometer is calibrated with full field of view, when the voltage saturation of the spectroradiometer reaches the upper limit, in order to make the spectroradiometer calibration data valid, the following conditions need to be met: the radiation flux P3 of the target at a certain distance is less than or equal to the radiation flux P1 of the surface source black body at the highest calibration temperature. That is:

[0058] p3≤p1 (20)

[0059] Combining equation (6), equation (19) and equation (20), we get the following equation:

[0060]

[0061] when When the target infrared radiation characteristic test distance R1 reaches the minimum value R 1min Therefore, it can be concluded that the minimum test distance R of the target infrared radiation characteristics is 1min for:

[0062]

[0063] At this point, the minimum test distance R of the target infrared radiation characteristic is obtained. 1min .

[0064] The above-mentioned method for selecting the minimum test distance of the target infrared radiation characteristics, the spectroradiometer is calibrated with the field of view filled, and is carried out in the laboratory; the spectroradiometer is calibrated with the field of view filled, the spectroradiometer begins to measure the radiation energy of the surface source blackbody radiation surface, and at the same time, the temperature of the surface source blackbody begins to gradually increase from room temperature. When the voltage saturation corresponding to the indium telluride channel on the spectroradiometer test software reaches the upper limit, the temperature T1 of the surface source blackbody at this time is recorded. The temperature T1 of the surface source blackbody at this time is the highest calibration temperature of the surface source blackbody when the spectroradiometer is calibrated with the field of view filled.

[0065] The above-mentioned method for selecting the minimum test distance of target infrared radiation characteristics, the step 7 of determining the preliminary minimum test distance of target infrared radiation characteristics further includes:

[0066] The full field of view area A2 of the spectroradiometer is related to the field of view angle θ of the spectroradiometer lens and the initial test distance. The specific relationship is as follows:

[0067]

[0068] In formula (15), R is the preliminary test distance of the target infrared radiation characteristics, that is, the distance from the spectroradiometer lens to the target radiation surface; 0.0573 is the conversion coefficient between radians and angles.

[0069] From the relationship between the target area ratio γ in the full field of view and the radiation emittance ratio obtained in step 6, it can be seen that when When the target infrared radiation characteristics are initially tested, the distance R reaches the minimum value R min , therefore, it can be concluded that:

[0070]

[0071] From formula (16), it can be further deduced that the initial minimum test distance R of the target infrared radiation characteristics is min Relationship with radiant emittance:

[0072]

[0073] At this point, the preliminary minimum test distance of the target infrared radiation characteristics is obtained.

[0074] The beneficial effects of the present invention are:

[0075] A method for selecting a minimum test distance for target infrared radiation characteristics is disclosed. According to the light flux propagation law of an optical imaging system and the law of conservation of radiation brightness of a lossless medium, and based on a method of comparing the saturation of a radiation flux response voltage value of a black body and a target radiation brightness on a detector image plane after the black body and the target radiation brightness pass through an optical system, the minimum test distance for target infrared radiation characteristics is determined. Through verification by an embodiment, the target infrared radiation characteristics test distance is determined, and a spectroradiometer is placed at the distance for testing. The voltage saturation corresponding to an indium telluride channel of the spectroradiometer tested is 97%, which is 98% compared with the voltage value saturation of 98% generated by the radiation flux response on the detector image plane after the high-temperature radiation brightness passes through the optical system when the spectroradiometer fills the field of view and is linearly calibrated. The relative error is 1%, and a beneficial effect is achieved. DETAILED DESCRIPTION

[0076] Example

[0077] A method for selecting a minimum test distance for target infrared radiation characteristics comprises the following steps:

[0078] Step 1: Determine the highest calibration temperature of the surface source blackbody when the spectroradiometer fills the field of view.

[0079] The spectroradiometer is used as the test equipment and the surface blackbody is used as the standard radiation source to calibrate the spectroradiometer to fill the field of view. The surface blackbody temperature when the voltage saturation of the indium telluride channel of the spectroradiometer reaches the upper limit is the highest calibration temperature of the surface blackbody when the spectroradiometer is calibrated to fill the field of view.

[0080] The spectroradiometer is calibrated with the field of view filled in the laboratory. The spectroradiometer is calibrated with the field of view filled in. The spectroradiometer starts to measure the radiation energy of the surface source blackbody radiation surface. At the same time, the temperature of the surface source blackbody starts to gradually increase from room temperature. When the voltage saturation corresponding to the indium telluride channel on the spectroradiometer test software reaches the upper limit, the temperature T1 of the surface source blackbody is recorded. The temperature T1 of the surface source blackbody at this time is the highest calibration temperature of the surface source blackbody when the spectroradiometer is calibrated with the field of view filled in.

[0081] For example, the laboratory temperature is room temperature, 22°C, and the laboratory humidity is 36%. The test equipment used is the MR170 spectroradiometer. The lens of the MR170 spectroradiometer uses a lens with a field of view angle of θ, a field of view angle of 28mrad, and the diameter of the spectroradiometer detector is 1mm and the detector area is ; The French FLUKE4181 surface source blackbody is used as the test target. The French FLUKE4181 surface source blackbody has a size of 150mm, a temperature accuracy of ±0.5℃, a stability of ±0.5℃, a spectral range of 2μm~15μm, and an emissivity of >0.95.

[0082] The MR170 spectroradiometer is calibrated with the field of view filled. When the MR170 spectroradiometer measures the radiation energy of the surface source blackbody radiation surface, the temperature of the surface source blackbody begins to gradually increase from room temperature. When the voltage saturation corresponding to the indium telluride channel on the spectroradiometer test software reaches 98%, the voltage saturation reaches the upper limit. At this time, the highest calibration temperature T1 of the surface source blackbody when the MR170 spectroradiometer is calibrated with the field of view filled is 187°C.

[0083] Step 2: Calculate the radiation emittance of the surface source blackbody at the highest calibration temperature

[0084] The radiation emittance M is calculated by Planck's formula, which is as follows:

[0085]

[0086] In formula (1), c1 is the first radiation constant, c1 = 3.7418 × 10 8 m / s, c2 is the second radiation constant, c2=1.4388×10 -16 W·m 2 , λ is the wavelength of the measurement band, T is the temperature of the standard radiation source, λ1 is the lower limit of the wavelength of the measurement band, and λ2 is the upper limit of the wavelength of the measurement band.

[0087] It can be inferred from formula (1) that the radiation emittance M1 of the surface source blackbody at the highest calibration temperature T1 is:

[0088]

[0089] At this point, the radiation emittance M1 of the surface source blackbody at the highest calibration temperature is obtained.

[0090] For example, the conditions are the same as those in step 1. When the highest calibration temperature of the surface source blackbody is 187°C and the measurement band is 2-5 μm, that is, the lower limit of the measurement band is 2 μm and the upper limit of the measurement band is 5 μm, the radiation emittance of the surface source blackbody at 187°C is calculated by formula (2) to be 305.7063 W·m -2 .

[0091] Step 3: Calculate the radiation flux function of the surface source blackbody at the highest calibration temperature

[0092] According to the propagation law of light flux in the optical imaging system, the radiation flux function of the standard radiation source projected onto the spectroradiometer detector through the optical system is:

[0093] P=βτLΩA (3)

[0094] In formula (3), P is the radiation flux projected onto the spectroradiometer detector through the optical system, β is the atmospheric transmittance, τ is the transmittance of the internal optical system of the spectroradiometer, L is the target spectral radiation brightness, Ω is the aperture angle of the internal optical system of the spectroradiometer, and A is the detector area of ​​the spectroradiometer.

[0095] When the surface source blackbody is at the highest calibration temperature, the radiation flux function of the surface source blackbody on the spectroradiometer detector is:

[0096] P1=β1τL1ΩA (4)

[0097] In formula (4), P1 is the radiation flux of the surface source black body projected onto the detector at the highest calibration temperature, that is, the radiation flux of the surface source black body at the highest calibration temperature; β1 is the atmospheric transmittance between the spectroradiometer and the surface source black body. Under ideal conditions, β1=1; L1 is the radiation brightness of the surface source black body at the highest calibration temperature.

[0098] According to the radiation characteristics of the radiation source, the radiation brightness of the surface source black body at the highest calibration temperature is related to the radiation emittance, and the relationship is as follows:

[0099]

[0100] Substituting equation (5) into equation (4), we can obtain the radiation flux function of the surface source blackbody at the highest calibration temperature, as shown below.

[0101]

[0102] At this point, the radiation flux function of the surface source blackbody at the highest calibration temperature is obtained.

[0103] Step 4: Calculate the target's radiant emittance

[0104] Taking any radiation source as the target and the spectroradiometer as the test equipment, the radiation emittance M2 of the target is related to the temperature T2 and the wavelength of the target, and the radiation emittance M2 of the target can be calculated by the following formula.

[0105]

[0106] In formula (7), T2 is the target temperature.

[0107] At this point, the radiation emittance M2 of the target is obtained.

[0108] For example, the conditions are the same as those in step 2. When the target temperature is 450°C and the wavelength is in the 2-5 μm band, the target radiation emittance is 6165.7 Wm according to formula (7): -2 .

[0109] Step 5: Calculate the radiation flux function of the target

[0110] When selecting the minimum test distance for the target's infrared radiation characteristics, the influence of atmospheric attenuation on radiation is not considered for the time being. The radiation flux function of the target at a certain distance reflected on the detector of the spectroradiometer is calculated. Since the target does not fill the field of view at a certain distance, the projection of the target on the detector of the spectroradiometer is also not full. When the area of ​​the target in the full field of view is γ, the area of ​​the target is A1, the full field of view area of ​​the spectroradiometer at a certain distance is A2, and the area of ​​the target projected onto the detector of the spectroradiometer is A b According to the symmetric relationship of the triangle ratio, the area ratio γ of the target in the whole field of view is proportional to the area A projected onto the detector of the spectroradiometer. b , the detector area A of the spectroradiometer; the relationship between the target area ratio γ in the full field of view and the target area A1 and the full field of view area A2 of the spectroradiometer at a certain distance is as follows:

[0111]

[0112]

[0113] According to the radiation characteristics of the radiation source, the radiation brightness of the target is related to the radiation emittance, and the relationship is as follows:

[0114]

[0115] According to the propagation law of light flux in the optical imaging system, when the target is at a certain distance during the spectroradiometer test, the radiation flux function projected onto the spectroradiometer detector through the optical system is:

[0116] P2=β2τL2ΩA b (11)

[0117] In formula (11), P2 is the radiation flux on the spectroradiometer detector when the target is at a certain distance, that is, the radiation flux of the target, and L2 is the radiation brightness of the target. The influence of atmospheric attenuation on radiation is not considered for the time being, that is, in the ideal state, β2 = 1.

[0118] By combining equations (8), (10) and (11), we can get the radiation flux function of the target as follows:

[0119]

[0120] At this point, the radiation flux function of the target is obtained.

[0121] Step 6: Determine the relationship between the target area ratio γ in the full field of view and the radiation emittance ratio

[0122] When the spectroradiometer is calibrated with full field of view, the voltage saturation of the spectroradiometer reaches the upper limit at the highest calibration temperature of the surface source black body. In order to make the calibration data of the spectroradiometer valid, the following conditions need to be met: the radiation flux P2 of the target is less than or equal to the radiation flux P1 of the surface source black body at the highest calibration temperature. That is:

[0123] p2≤p1 (13)

[0124] Combining equation (6), equation (12) and equation (13), we get the following equation:

[0125]

[0126] Formula (14) is the relationship between the target area ratio γ in the whole field of view and the radiation emittance ratio.

[0127] Step 7: Determine the initial minimum test distance of the target infrared radiation characteristics

[0128] The full field of view area A2 of the spectroradiometer is related to the field of view angle θ of the spectroradiometer lens and the initial test distance. The specific relationship is as follows:

[0129]

[0130] In formula (15), R is the preliminary test distance of the target infrared radiation characteristics, that is, the distance from the spectroradiometer lens to the target radiation surface; 0.0573 is the conversion coefficient between radians and angles.

[0131] From the relationship between the target area ratio γ in the full field of view and the radiation emittance ratio obtained in step 6, it can be seen that when When the target infrared radiation characteristics are initially tested, the distance R reaches the minimum value R min , therefore, it can be concluded that:

[0132]

[0133] From formula (16), it can be further deduced that the minimum distance R for preliminary test of target infrared radiation characteristics is min Relationship with radiant emittance:

[0134]

[0135] At this point, the preliminary minimum test distance of the target infrared radiation characteristics is obtained.

[0136] For example, the conditions are the same as in step 4. The spectroradiometer lens uses a θ = 28mrad lens and the target size is Φ = 150mm, that is, Substituting the results obtained in step 2 and step 4 into equation (17), we can obtain the preliminary minimum test distance of the target infrared radiation characteristics as 24.0555 meters.

[0137] Step 8: Determine the minimum test distance of the target infrared radiation characteristics

[0138] When actually measuring the infrared radiation characteristics of a target, that is, under non-ideal conditions, the influence of atmospheric transmittance should be considered.

[0139] The initial minimum test distance of the target infrared radiation characteristics obtained in step 7 is calculated by taking into account the influence of atmospheric transmittance. min The atmospheric radiation transmission characteristics calculation software MODTRAN is used to generate the atmospheric transmittance β3 at the preliminary minimum test distance.

[0140] According to the propagation law of light flux in the optical imaging system, when the target is at a certain distance and the influence of atmospheric transmittance is considered during the spectroradiometer test, the radiation flux function projected onto the spectroradiometer detector through the optical system is:

[0141] P3=β3τL2ΩA b (18)

[0142] In formula (18), P3 is the radiation flux on the detector when the target is at a certain distance considering the atmospheric transmittance, and β3 is the atmospheric transmittance between the spectroradiometer and the target.

[0143] By combining equation (8), equation (10) and equation (18), we can get the following equation:

[0144]

[0145] Formula (19) is the radiation flux function when the target is at a certain distance.

[0146] When the spectroradiometer is calibrated with full field of view, when the voltage saturation of the spectroradiometer reaches the upper limit, in order to make the spectroradiometer calibration data valid, the following conditions need to be met: the radiation flux P3 of the target at a certain distance is less than or equal to the radiation flux P1 of the surface source black body at the highest calibration temperature. That is:

[0147] p3≤p1 (20)

[0148] Combining equation (6), equation (19) and equation (20), we get the following equation:

[0149]

[0150] when When the target infrared radiation characteristic test distance R1 reaches the minimum value R 1min , therefore, it can be concluded that:

[0151]

[0152] In formula (22), R 1min It is the minimum test distance of the target infrared radiation characteristics.

[0153] From formula (22), it can be further deduced that the minimum test distance R of the target infrared radiation characteristic is 1min The relationship with radiation emittance and atmospheric transmittance is as follows:

[0154]

[0155] At this point, the minimum test distance R of the target infrared radiation characteristic is obtained. 1min .

[0156] For example, the conditions are the same as those in step 7. The preliminary minimum test distance determined by step 7 is 24.0555 meters. According to the atmospheric radiation transmission characteristic calculation software MODTRAN, the atmospheric transmittance between the spectroradiometer and the target at the preliminary minimum test distance is calculated to be 0.83665. Substituting the results obtained in steps 2 and 4 into formula (23), the minimum test distance of the target infrared radiation characteristic can be obtained to be 22.003 meters.

Claims

1. A method for selecting the minimum test distance of target infrared radiation characteristics, characterized in that: The steps include: Step 1: Determine the highest calibration temperature of the surface source blackbody when the spectroradiometer fills the field of view: Using the spectroradiometer as the test equipment and the surface source blackbody as the standard radiation source, the spectroradiometer is calibrated to fill the field of view. When the voltage saturation of the indium telluride channel of the spectroradiometer reaches the upper limit, the surface source blackbody temperature is the highest calibration temperature T1 of the surface source blackbody when the spectroradiometer fills the field of view for calibration; Step 2, calculate the radiation emittance of the surface source blackbody at the highest calibration temperature: The radiation emittance M1 of the surface source blackbody at the highest calibration temperature T1 is: In formula (2), c1 is the first radiation constant, c1 = 3.7418 × 10 8 m / s, c2 is the second radiation constant, c2=1.4388×10 -16 W·m 2 , λ is the wavelength of the measurement band, λ1 is the lower limit of the wavelength of the measurement band, and λ2 is the upper limit of the wavelength of the measurement band; Step 3, calculate the radiation flux function of the surface source blackbody at the highest calibration temperature: According to the propagation law of light flux in the optical imaging system, the radiation flux function of the standard radiation source projected onto the spectroradiometer detector through the optical system is: P=βτLΩA (3) In formula (3), P is the radiation flux projected onto the spectroradiometer detector through the optical system, β is the atmospheric transmittance, τ is the transmittance of the internal optical system of the spectroradiometer, L is the target spectral radiation brightness, Ω is the aperture angle of the internal optical system of the spectroradiometer, and A is the detector area of ​​the spectroradiometer; When the surface source blackbody is at the highest calibration temperature, the radiation flux function of the surface source blackbody on the spectroradiometer detector is: P1=β1τL1ΩA (4) In formula (4), P1 is the radiation flux of the surface source black body projected onto the detector at the highest calibration temperature, that is, the radiation flux of the surface source black body at the highest calibration temperature; β1 is the atmospheric transmittance between the spectroradiometer and the surface source black body. Under ideal conditions, β1 = 1; L1 is the radiation brightness of the surface source black body at the highest calibration temperature; According to the radiation characteristics of the radiation source, the radiation brightness of the surface source black body at the highest calibration temperature is related to the radiation emittance, and the relationship is as follows: Substituting equation (5) into equation (4), we can obtain the radiation flux function of the surface source blackbody at the highest calibration temperature, as follows: At this point, the radiation flux function of the surface source blackbody at the highest calibration temperature is obtained; Step 4, calculate the radiation emittance of the target: Take any radiation source as the target and the spectroradiometer as the test equipment; the radiation emittance M2 of the target is related to the temperature T2 and the waveband of the target. The radiation emittance M2 of the target can be calculated by the following formula: In formula (7), T2 is the target temperature; Step 5, calculate the radiation flux function of the target: When selecting the minimum test distance for the target's infrared radiation characteristics, the influence of atmospheric attenuation on radiation is not considered for the time being. The radiation flux function of the target at a certain distance reflected on the detector of the spectroradiometer is calculated. Since the target does not fill the field of view at a certain distance, the projection of the target on the detector of the spectroradiometer is also not full. When the area of ​​the target in the full field of view is γ, the area of ​​the target is A1, the full field of view area of ​​the spectroradiometer at a certain distance is A2, and the area of ​​the target projected onto the detector of the spectroradiometer is A b According to the symmetric relationship of the triangle ratio, the area ratio γ of the target in the whole field of view is proportional to the area A projected onto the detector of the spectroradiometer. b , the detector area A of the spectroradiometer; the relationship between the target area ratio γ in the full field of view and the target area A1 and the full field of view area A2 of the spectroradiometer at a certain distance is as follows: According to the radiation characteristics of the radiation source, the radiation brightness of the target is related to the radiation emittance, and the relationship is as follows: According to the propagation law of light flux in the optical imaging system, when the target is at a certain distance during the spectroradiometer test, the radiation flux function projected onto the spectroradiometer detector through the optical system is: P2=β2τL2ΩA b (11) In formula (11), P2 is the radiation flux on the detector of the spectroradiometer when the target is at a certain distance, that is, the radiation flux of the target, and L2 is the radiation brightness of the target; the influence of atmospheric attenuation on radiation is not considered for the time being, that is, in the ideal state, β2 = 1; By combining equations (8), (10) and (11), we can get the radiation flux function of the target as follows: Step 6: Determine the relationship between the target area ratio γ in the full field of view and the radiation emittance ratio: When the spectroradiometer is calibrated with full field of view, the voltage saturation of the spectroradiometer reaches the upper limit at the highest calibration temperature of the surface source blackbody. In order to make the calibration data of the spectroradiometer valid, the following conditions need to be met: the radiation flux P2 of the target is less than or equal to the radiation flux P1 of the surface source blackbody at the highest calibration temperature; that is: p2≤p1 (13) Combining equation (6), equation (12) and equation (13), we get the following equation: Formula (14) is the relationship between the target area ratio γ in the full field of view and the radiation emittance ratio; Step 7: Determine the initial minimum test distance of the target infrared radiation characteristics: According to the relationship between the target area ratio γ in the full field of view and the radiation emittance ratio, the initial minimum test distance R of the target infrared radiation characteristics is determined. min ; Step 8: Determine the minimum test distance of the target infrared radiation characteristics: When actually measuring the infrared radiation characteristics of the target, that is, under non-ideal conditions, the influence of atmospheric transmittance should be considered; The initial minimum test distance of the target infrared radiation characteristics obtained in step 7 is calculated by taking into account the influence of atmospheric transmittance. min Bring it into the atmospheric radiation transmission characteristics calculation software MODTRAN to generate the atmospheric transmittance β3 at the preliminary minimum test distance; According to the propagation law of light flux in the optical imaging system, when the target is at a certain distance and the influence of atmospheric transmittance is considered during the spectroradiometer test, the radiation flux function projected onto the spectroradiometer detector through the optical system is: P3=β3τL2ΩA b (18) In formula (18), P3 is the radiation flux on the detector when the target is at a certain distance considering the atmospheric transmittance, and β3 is the atmospheric transmittance between the spectroradiometer and the target; By combining equation (8), equation (10) and equation (18), we can get the following equation: Formula (19) is the radiation flux function when the target is at a certain distance; When the spectroradiometer is calibrated with full field of view, when the voltage saturation of the spectroradiometer reaches the upper limit, in order to make the spectroradiometer calibration data valid, the following conditions need to be met: the radiation flux P3 of the target at a certain distance is less than or equal to the radiation flux P1 of the surface source blackbody at the highest calibration temperature; that is: p3≤p1 (20) Combining equation (6), equation (19) and equation (20), we get the following equation: when When the target infrared radiation characteristic test distance R1 reaches the minimum value R 1min Therefore, it can be concluded that the minimum test distance R of the target infrared radiation characteristics is 1min for: At this point, the minimum test distance R of the target infrared radiation characteristic is obtained. 1min .

2. The method for selecting the minimum test distance of target infrared radiation characteristics according to claim 1, characterized in that: The spectroradiometer is calibrated with the field of view filled, and is carried out in a laboratory. The spectroradiometer is calibrated with the field of view filled, and the spectroradiometer starts to measure the radiation energy of the surface source blackbody radiation surface. At the same time, the temperature of the surface source blackbody starts to gradually increase from room temperature. When the voltage saturation corresponding to the indium telluride channel on the spectroradiometer test software reaches the upper limit, the temperature T1 of the surface source blackbody at this time is recorded. The temperature T1 of the surface source blackbody at this time is the highest calibration temperature of the surface source blackbody when the spectroradiometer is calibrated with the field of view filled.

3. The method for selecting the minimum test distance of target infrared radiation characteristics according to claim 1, characterized in that: The step 7, determining the preliminary minimum test distance of the target infrared radiation characteristic, further comprises: The full field of view area A2 of the spectroradiometer is related to the field of view angle θ of the spectroradiometer lens and the initial test distance. The specific relationship is as follows: In formula (15), R is the initial test distance of the target infrared radiation characteristics, that is, the distance from the spectroradiometer lens to the target radiation surface; 0.0573 is the conversion coefficient between radians and angles; From the relationship between the target area ratio γ in the full field of view obtained in step 6 and the radiation emittance ratio, we can know that when When the target infrared radiation characteristics are initially tested, the distance R reaches the minimum value R min , therefore, it can be concluded that: From formula (16), it can be further deduced that the initial minimum test distance R of the target infrared radiation characteristics is min Relationship with radiant emittance: At this point, the preliminary minimum test distance of the target infrared radiation characteristics is obtained.

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