Strong-sky-background-oriented space target temperature inversion system and method

Abstract

The invention belongs to the technical field of space target temperature inversion, and particularly relates to a space target temperature inversion system and method for a strong skylight background. The method comprises the following steps: S1, obtaining an infrared radiation response rate and an atmospheric extinction coefficient of a space target temperature inversion system based on an atmospheric extinction model, and calculating the irradiance of a to-be-measured target under each spectrum channel of a high-speed rotating filter wheel based on the infrared radiation response rate and the atmospheric extinction coefficient; s2, on the basis of the irradiance under each spectrum channel, constructing a function relation between the material emissivity and the surface temperature of the target surface element under each spectrum channel; and S3, based on the function relation in the step S2, a blind optimization algorithm is adopted to solve the radiation brightness under each spectrum channel, and a temperature inversion result of the to-be-measured target is obtained. According to the invention, blind optimization is carried out on the material emissivity of a material spectrum, real-time detection of a space low-temperature target is realized, and temperature distribution of complex materials (emissivity of different materials) is inverted.

Description

Technical Field

[0001] The present invention belongs to the technical field of space target temperature inversion, and in particular relates to a space target temperature inversion system and method facing a strong skylight background. Background Art

[0002] For ground-based optoelectronic detection equipment, the infrared detection system is an important optoelectronic sensing terminal for obtaining the radiation characteristics of the target. It can be used to analyze the changes in the surface temperature distribution of space targets and the heating characteristics of the internal power source over time, and provide information support for applications such as target feature extraction, state judgment, and fault diagnosis.

[0003] However, the temperature of space targets is relatively low (usually around 220-360K) and the observation distance is far, resulting in weak infrared radiation characteristic signals. Under the influence of strong daylight background, the time-varying contrast between the photon flux of space targets and the background photon noise is very low, making it difficult for the infrared detection system to extract the radiation characteristics of space targets. On the other hand, planar targets have complex materials, and the system lacks prior information such as material emissivity, and unknown changes may occur due to factors such as oxidation and attitude adjustment, further increasing the difficulty of accurately inverting component temperature.

[0004] Traditional methods obtain the temperature of space targets through full-band temperature measurement, colorimetric temperature measurement, spectral measurement, and multi-band radiation temperature measurement, but they are not sufficient to meet the application requirements of temperature inversion for space targets with low temperature, low signal-to-noise ratio, and complex materials.

[0005] With the rapid development of space science and technology, the number of artificial celestial bodies in space has increased dramatically. As of now, the number of artificial satellites in orbit has exceeded 19,000. It is of great significance to analyze and judge the operation status of artificial satellites in orbit. However, the temperature of space targets is relatively low (usually around 220-360K), the observation distance is far, the infrared radiation characteristic signal is weak, and there is a lack of prior information such as material emissivity, which seriously affects the accuracy of obtaining the surface temperature distribution of space targets and the heating characteristics of internal power sources.

[0006] Existing technologies use full-band temperature measurement, colorimetric temperature measurement, spectral temperature measurement, and multi-band radiation temperature measurement methods, but it is difficult to continuously obtain the temperature distribution map of low-temperature space targets and infrared radiation characteristic density areas in complex sky areas, and cannot meet the application requirements of component temperature warning for space targets with low temperature, low signal-to-noise ratio, and complex materials.

[0007] The full-band temperature measurement method is suitable for known target effective surface area and all wavelength radiation material emissivity. The temperature of the space target is determined by integrating all radiation energy in the detection direction. It is impossible to obtain temperature and other information for targets with unknown material spectrum and material emissivity.

[0008] The colorimetric temperature measurement method obtains the target temperature through the ratio of the radiation brightness between multiple bands and the theoretical ratio of the energy between different bands. This method takes into account the continuity of the spectral material emissivity of the material, and reduces the error caused by the unknown true value in temperature inversion through the ratio of the radiation brightness between multiple bands, but it also requires a higher signal-to-noise ratio for the space target. Especially for low-temperature targets whose radiation brightness is often lower than 1, the ratio relationship will introduce large noise, causing the annihilation of the temperature signal of the space target and unclear edges.

[0009] Spectral temperature measurement usually uses prism or grating to obtain sufficient spectral data, and then fits the spectral data based on the Planck function to calculate the equivalent temperature and equivalent area of ​​the space target. However, this method is difficult to extract accurate information about each component of the space target, and the number of spectral measurements limits the signal-to-noise ratio of spectral measurement.

[0010] The multi-band radiation temperature measurement method combines parameters such as path radiation, atmospheric attenuation and system transmittance to estimate the material emissivity, and then inverts the target temperature through the target radiation brightness. However, multi-band temperature inversion is a mathematically ill-posed problem, that is, the number of unknown parameters is greater than the number of measurement equations. The unclear a priori information on material emission leads to inaccurate temperature measurement by this method. Summary of the invention

[0011] In view of this, the invention aims to provide a space target temperature inversion system and method for strong sky background, so as to solve the problem that it is difficult to continuously obtain the temperature of low-temperature space targets and the distribution map of infrared radiation characteristic density area under complex sky areas, and cannot meet the application requirements of component temperature warning for space targets with low temperature, low signal-to-noise ratio and complex materials. The present invention blindly optimizes the material spectral material emissivity, realizes real-time detection of low-temperature targets in space, and inverts the temperature distribution of complex materials (different material emissivities).

[0012] To achieve the above object, the technical solution created by the present invention is implemented as follows: A temperature inversion system for space targets facing a strong skylight background comprises a telescope optical module, a cold optical infrared spectrum module, an infrared detector and a data processing module. The telescope optical module collects light signals of a target to be measured, and the light signals are incident on the infrared detector through the cold optical infrared spectrum module for imaging, so as to obtain a multi-band infrared image of the target. The infrared detector also sends the target infrared image to the data processing module. The data processing module uses an infrared standard star to perform infrared calibration on the target to be measured, and uses a blind optimization algorithm to process the infrared calibration result, so as to realize temperature inversion of the target to be measured.

[0013] Furthermore, the cold optical infrared spectrum module includes a low-temperature Dewar, and a long-wave attenuation plate, a first long-wave lens assembly, a second long-wave lens assembly and a high-speed rotating filter wheel placed inside the low-temperature Dewar. The light signal incident on the low-temperature Dewar is incident on the infrared detector via the long-wave attenuation plate, the first long-wave lens assembly, the second long-wave lens assembly and the high-speed rotating filter wheel in sequence.

[0014] Furthermore, the first long-wave lens assembly and the second long-wave lens assembly have the same structure, both comprising a translation platform and an optical element for secondary imaging, the optical element being placed on the translation platform, and the translation platform driving the optical element to move relative to the telescope optical module.

[0015] Furthermore, the long-wave attenuation plate can transmit a light beam of 8-12 microns; the high-speed rotating filter wheel includes a plurality of narrow-band filters, and each narrow-band filter corresponds to a spectral channel of a wavelength band.

[0016] A space target temperature inversion method for a strong skylight background is implemented by using a space target temperature inversion system for a strong skylight background. The space target temperature inversion system includes a high-speed rotating filter wheel, and specifically includes the following steps: S1: Based on the atmospheric extinction model, the infrared radiation response rate and atmospheric extinction coefficient of the space target temperature inversion system are obtained, and the radiant illumination of the target to be measured under each spectral channel of the high-speed rotating filter wheel is calculated based on the infrared radiation response rate and the atmospheric extinction coefficient; S2: Based on the radiant illumination in each spectral channel, a functional relationship between the material emissivity and the surface temperature of the target surface element in each spectral channel is constructed; S3: Based on the functional relationship of step S2, a blind optimization algorithm is used to solve the radiation brightness under each spectral channel to obtain the temperature inversion result of the target to be measured.

[0017] Furthermore, step S1 specifically includes the following steps: S11: Based on the atmospheric extinction model, invert the radiance of the infrared standard star: (1); (2); (3); in, is the pixel response value of the infrared detector after removing the atmospheric background, is the pixel bias of the infrared detector, is the irradiance of the target to be measured, is the response rate of the infrared detector pixel to the radiation illumination, is the atmospheric transmittance of the target to be measured at the zenith angle θ, is the atmospheric transmittance factor, is the atmospheric extinction model, is the atmospheric extinction optical thickness in the vertical direction, For air quality, is the zenith angle in degrees, λ is the central wavelength of the current spectral channel, is the target light intensity of the target to be measured; S12: Take the logarithm of equation (1): (4); S13: Use the least squares method to fit equation (4) to obtain the atmospheric extinction coefficient and infrared radiation response rate , based on the atmospheric extinction coefficient and infrared radiation response rate Update formula (4); S14: adjusting the high-speed rotating filter wheel to the first spectral channel, using the space target temperature inversion system to measure the target to be measured, obtaining the zenith angle of the target to be measured, substituting the zenith angle of the target to be measured into the updated formula (4) for calculation, and obtaining the radiant illumination of the target to be measured under the current spectral channel; S15: replacing the first spectral channel with the second spectral channel of the high-speed rotating filter wheel, and repeating step S14 until the radiant illumination of the target to be measured under each spectral channel is obtained.

[0018] Furthermore, step S2 specifically includes the following steps: S21: Calculate the radiation solid angle Ω corresponding to a single pixel of the infrared detector: (5); in, is the area of ​​a single pixel in the focal plane array of the infrared detector, is the angle between the main optical line of the radiation and the main optical axis, is the focal length of the space target temperature inversion system; S22: Based on the mapping relationship between the face element of the target to be measured and the pixel of the infrared detector, set , combined with formula (5), the radiation brightness of the target to be measured in the detection direction is obtained: (6); in, is the radiation brightness L obtained by the i-th pixel incident on the i-th pixel of the infrared detector through the spectral channel with a central wavelength of λ, is the radiant illumination obtained by the i-th pixel of the infrared detector incident on the i-th pixel through the spectral channel with a central wavelength of λ; S23: Apply formula (6) to obtain the radiant brightness Substituting into Planck's law, we can obtain the functional relationship between the material emissivity and surface temperature of the target surface element: (7); in, is the material emissivity of the i-th surface element included in the target surface element, is the first radiation constant, which is 3.742×10 -16 W·m 2 , is the second radiation constant, which is 1.4388×10 -2 m·K, is the surface temperature of the i-th element in the spectral channel with the central wavelength λ.

[0019] Furthermore, step S3 specifically includes the following steps: S31: Set initial material emissivity and a fixed gain factor γ; S32: Set the initial material emissivity under each spectral channel Same as the initial material emissivity Substituting into equation (7), we can obtain the surface temperature of each facet under each spectral channel; S33: Take the average of the surface temperatures of all the facets and calculate the performance evaluation index using the following formula: (8); Among them, J i is the performance evaluation index of the i-th facet, is the central wavelength of the narrowband filter, m is the total number of narrowband filters, is the i-th element at the central wavelength The surface temperature calculated under the spectral channel is i is the average temperature of the i-th element calculated under each narrowband filter; S34: Generate random perturbation material emission rate in the interval [0, 1] that conforms to the Bernoulli distribution , using the first emission value Replace the initial material emissivity in step S32 , repeat steps S32-S33 to obtain the first performance evaluation index; use the second emission value Replace the initial material emissivity in step S32 , repeat steps S32-S33 to obtain a second performance evaluation index; take the difference between the first performance evaluation index and the second performance evaluation index as the evaluation coefficient N; S35: If , then the surface temperature of each facet corresponding to each spectral channel is obtained, and the temperature inversion of the target to be measured is completed. Otherwise, the initial material emissivity of step S32 is replaced by the next material emissivity, and steps S32-S34 are repeated until So far, the surface temperature of each facet corresponding to each spectral channel is obtained, and the temperature inversion of the target to be measured is completed.

[0020] Further, in step S35, the next material emissivity The calculation formula is: (9); in, is the iteration step length, is the difference between the evaluation factors of the first emission value and the second emission value, The material emissivity difference between the first emissivity value and the second emissivity value.

[0021] Further, in step S35, <1.

[0022] Compared with the prior art, the invention can achieve the following beneficial effects: (1) The temperature inversion system and method for space targets facing a strong skylight background created by the present invention minimizes the influence of stray light outside the field of view by arranging light-blocking rings and light shields at the primary lens barrel, the periphery of the secondary mirror, and the center of the primary mirror of the telescope optical module.

[0023] (2) The system and method for temperature inversion of space targets facing strong skylight background created by the present invention adopts a space target temperature inversion system (a cold optical infrared detection system consisting of a low-temperature dewar, a long-wave attenuation plate, a first long-wave lens assembly, a second long-wave lens assembly, a high-speed rotating filter wheel and an infrared detector), which reduces background infrared radiation noise and realizes multi-spectral and high-resolution infrared imaging of low-temperature space targets.

[0024] (3) The system and method for temperature inversion of space targets facing strong skylight background created by the present invention adopt a blind optimization algorithm to blindly optimize and correct the material spectral material emissivity, thereby reducing the influence of unknown material emissivity on the inversion accuracy of equivalent temperatures of different components, and realizing the acquisition of temperature distribution of complex materials of low-temperature targets.

[0025] (4) The present invention creates a space target temperature inversion system and method for strong skylight background, which uses a space target temperature inversion system (cold optical infrared detection system) to image the radiation characteristics of space targets, and uses the difference in infrared multi-band radiation brightness caused by the deviation of material emissivity, combined with a blind optimization algorithm (such as a random parallel gradient descent algorithm) to blindly optimize and correct the material spectral material emissivity, thereby improving the accuracy of temperature inversion for different components of space targets (different material emissivity). Compared with traditional methods, the present invention does not need to use the known material emissivity as prior information, nor does it need to make high requirements on the target signal-to-noise ratio. By using the continuity of the emissivity of adjacent spectral materials and the true error of the spectral material emissivity to reduce the difference caused by the multi-band spectral radiation brightness, combined with a blind optimization algorithm to optimize and correct the material emissivity at the pixel level, and obtain information such as the target surface temperature distribution and the heating characteristics of the internal power source, it is expected to greatly improve the precision and accuracy of the temperature inversion of the infrared detector and realize the temperature warning of the space target components. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings: Figure 1 A schematic diagram of the structure of a space target temperature inversion system facing a strong skylight background according to an embodiment of the present invention; Figure 2 A schematic diagram of the flow of a method for inverting temperature of a space target facing a strong skylight background as described in an embodiment of the present invention; Figure 3 A schematic diagram of the monochromator scanning calibration structure according to an embodiment of the present invention; Figure 4 To create a target temperature deviation curve of the preset material emissivity of the space target described in the embodiment of the present invention and the inversion of each spectral channel;.

[0027] Description of reference numerals: 1. Primary mirror; 2. Secondary mirror; 3. Secondary mirror diaphragm; 4. Primary mirror tube light-blocking ring; 5. Primary mirror diaphragm; 6. Low-temperature Dewar; 7. Long-wave attenuation plate; 8. First long-wave lens assembly; 9. Second long-wave lens assembly; 10. High-speed rotating filter wheel; 11. Infrared detector; 12. Data processing module; 13. Silicon carbon rod; 14. Entrance slit; 15. Collimator; 16. Grating; 17. Focusing mirror; 18. Exit slit; 19. Collimator. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0029] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0031] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0032] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0033] like Figure 1As shown, the temperature inversion system for space targets facing strong skylight background proposed by the present invention includes a telescope optical module, a cold optical infrared spectrum module, an infrared detector 11 and a data processing module 12. The telescope optical module collects the optical signal of the target to be measured, and the optical signal is incident on the infrared detector 11 through the cold optical infrared spectrum module for imaging to obtain a multi-band target infrared image. The infrared detector 11 also sends the target infrared image to the data processing module 12. The data processing module 12 uses an infrared standard star to perform infrared calibration on the target to be measured, and uses a blind optimization algorithm (the blind optimization algorithm includes a random parallel gradient descent algorithm (SPGD algorithm), a genetic algorithm, a difference algorithm and an annealing algorithm) to process the infrared calibration result to achieve temperature inversion of the target to be measured.

[0034] The detailed structure of the above-mentioned module is introduced below. The telescope optical module includes a primary mirror 1, a secondary mirror 2, a secondary mirror diaphragm, a primary mirror barrel light-blocking ring and a primary mirror light-blocking barrel. The incident light is incident on the secondary mirror 2 through the primary mirror 1, and the light reflected by the secondary mirror 2 is incident on the cold optical infrared spectrum module through the primary mirror 1. The primary mirror 1 and the secondary mirror 2 adopt a Cassegrain structure. The primary mirror 1 is provided with a primary mirror barrel light-blocking ring, and the secondary mirror 2 is placed inside the primary mirror barrel light-blocking ring. The inner wall of the barrel of the primary mirror 1 extends outward and exceeds the secondary mirror 2. A plurality of light-blocking rings are arranged on the inner wall of the barrel to form a main mirror barrel light-blocking ring to reduce the influence of stray light outside the field of view. The primary mirror 1 is also provided with a primary mirror shading tube, which is located between the primary mirror 1 and the secondary mirror 2 and is used to suppress stray light outside the light beam transmitted between the primary mirror 1 and the secondary mirror 2. The secondary mirror 2 is provided with a secondary mirror shading stop, and the secondary mirror shading stop, the primary mirror tube light blocking ring and the primary mirror shading tube are combined to suppress stray light, so as to reduce the influence of stray light on the image processing at the back end. The telescope optical module is mainly responsible for the signal acquisition and transmission of space targets and the suppression of stray light outside the field of view. The signal of the space target is reflected by the primary and secondary mirrors 2 to the cold optical infrared detection system (including the cold optical infrared spectrum module, the infrared detector 11 and the data processing module 12) at the back end for processing.

[0035] The cold optical infrared spectrum module includes a low temperature dewar 6, and a long wave attenuation plate 7, a first long wave lens assembly 8, a second long wave lens assembly 9 and a high-speed rotating filter wheel 10 placed inside the low temperature dewar 6. The light signal incident on the low temperature dewar 6 is incident on the infrared detector 11 through the long wave attenuation plate 7, the first long wave lens assembly 8, the second long wave lens assembly 9 and the high-speed rotating filter wheel 10 in sequence. The low temperature dewar 6 is equipped with a vacuum valve interface, which is connected to a molecular pump through a KF flange to make the vacuum degree in the cavity reach 10 - 3Pa, using two 15W@77K (-196℃) gas bearing Stirling refrigerators to stabilize the cavity temperature at 120K, reduce background infrared radiation noise, and achieve multi-spectral and high-resolution infrared imaging of low-temperature space targets. The light beam reflected by the target to be measured passes through the telescope optical module and is incident on the long-wave attenuation plate 7 inside the low-temperature Dewar 6. The long-wave attenuation plate 7 can transmit 8-12 micron light beams. The first long-wave lens assembly 8 and the second long-wave lens assembly 9 have the same structure, both including a displacement stage and an optical lens. The material emissivity optical lens is placed on the material emissivity displacement stage, and the displacement stage drives the optical lens to move relative to the telescope optical module. The first long-wave lens assembly 8 and the second long-wave lens assembly 9 have one-dimensional freedom adjustment capability, which is used to compensate for the defocus caused by temperature changes in the telescope optical module during imaging. The high-speed rotating filter wheel 10 is mainly composed of a servo motor, a motor seat, a coupling, a magnetic fluid, a filter wheel, etc. The filter wheel includes multiple filters, each filter transmits a band of light, that is, corresponds to a spectral channel of a band, and each filter can transmit light of different bands, so that the infrared detector 11 can quickly switch the filter during the high-frequency exposure process to obtain a multi-band target infrared image. After the light beam is attenuated, it passes through the imaging lens group inside the low-temperature dewar 6 and hits the camera target surface of the infrared detector 11, realizing the unknown matching of the main mirror 1 and the camera cold stop, and the filter is rotated by the filter wheel, and is synchronously exposed with the corresponding infrared detector 11 to complete the infrared band multi-spectral imaging of the space target.

[0036] The data processing module 12 is used to realize the infrared calibration and temperature inversion functions. First, the infrared radiation of the target to be measured is calibrated in real time through the infrared standard satellite, and the infrared radiation response rate and atmospheric extinction coefficient of the space target temperature inversion system are obtained to improve the accuracy of the infrared radiation illumination measurement of the space target. Then, the long-wave refrigeration type infrared detector 11 is used to detect the space target and obtain the measured multi-band infrared image of the target. The material emissivity is proposed, and the radiation brightness of each pixel of the infrared detector 11 is calculated. The temperature difference of the multi-band inversion is used as the evaluation factor of the space target temperature inversion system. The material emissivity is blindly optimized in combination with the blind optimization algorithm (random parallel gradient descent algorithm), so that the multi-band temperature standard deviation is stable and less than 5K, reducing the influence of the unclear prior information of the material emission on the temperature measurement, and completing the system convergence, thereby realizing the inversion of the temperature distribution map of the space target with complex materials (different material emissivities), low temperature and low signal-to-noise ratio.

[0037] like Figure 2 As shown, the space target temperature inversion method for strong skylight background provided by the present invention is implemented by using the space target temperature inversion system for strong skylight background, and specifically includes the following steps: S1: Obtain the infrared radiation response rate and the atmospheric extinction coefficient of the space target temperature inversion system based on the atmospheric extinction model, and calculate the radiant illumination of the target to be measured under each spectral channel of the high-speed rotating filter wheel 10 based on the infrared radiation response rate and the atmospheric extinction coefficient.

[0038] Infrared calibration includes spectral calibration and radiation calibration, the purpose of which is to determine the central wavelength of each spectral channel and the response of different wavelengths, and to establish a quantitative relationship between the incident radiation illumination of the target to be measured and the pixel grayscale response value of the target infrared image.

[0039] S11: The central wavelength, spectral response range and wavelength response curve of each spectral channel of the high-speed filter wheel are calibrated by using a monochromator scanning calibration method to achieve spectral calibration.

[0040] like Figure 3 As shown, the structure of the monochromator mainly includes an incident slit 14, a collimator 15, a grating 16, a focusing mirror 17 and an exit slit 18. During the calibration process, the scanning wavelength range of the monochromator, the width of the incident slit 14 and the width of the exit slit 18 are first set through the monochromator control software. The light emitted by the silicon carbon rod 13 is evenly irradiated on the incident slit 14 of the monochromator, and is adjusted to parallel light by the collimator 15. The parallel light is reflected by the grating 16 to produce multi-level diffraction monochromatic parallel light, and then passes through the focusing mirror 17 to the exit slit 18. The light emitted from the slit is adjusted to parallel light by the off-axis parabolic mirror of the collimator 19, and enters the cold optical infrared spectrum module, the infrared detector 11 and the data processing module 12 in sequence after signal modulation. The high-speed rotating filter wheel 10 is adjusted so that the light emitted by the monochromator can be irradiated on each spectral channel, and the wavelength and pixel grayscale response value of the infrared detector's response during the monochromator scanning process are recorded to draw a wavelength response curve; the wavelength response curve is fitted by a Gaussian function to determine the central wavelength and spectral response range of each spectral channel of the high-speed filter wheel.

[0041] Next, perform radiation calibration: S12: Select multiple infrared standard stars from the infrared standard star catalog, the extended catalog 2MASS, the extended catalog MSM and the extended catalog Spitzer. The multiple infrared standard stars are located at different zenith angles (10°-80°), and the selected infrared standard stars are calibrated using the space target temperature inversion system; After completing the S11-S12 work, the radiation calibration results will be more accurate.

[0042] S13: Based on the atmospheric extinction model, invert the radiance of the infrared standard star: (1); (2); (3); in, is the pixel response value of the infrared detector 11 after removing the atmospheric background, is the pixel bias of the infrared detector 11, is the irradiance of the target to be measured, is the response rate of the pixel of the infrared detector 11 to the radiation illumination, is the atmospheric transmittance of the target to be measured at the zenith angle θ, is the atmospheric transmittance factor, is the atmospheric extinction model, is the atmospheric extinction optical thickness in the vertical direction, For air quality, is the zenith angle in degrees, λ is the central wavelength of the current spectral channel, is the target light intensity of the target to be measured; S14: Take the logarithm of equation (1): (4); Top distance of the day When the temperature is less than 75°, the atmosphere can be approximately regarded as a plane parallel layer, and the calculation formula of the atmospheric mass is: ,otherwise The value remains unchanged.

[0043] S15: Use the least squares method to fit equation (4) to obtain the atmospheric extinction coefficient and infrared radiation response rate , based on the atmospheric extinction coefficient and infrared radiation response rate Update formula (4); S16: adjusting the high-speed rotating filter wheel 10 to the first spectral channel, using the space target temperature inversion system to measure the target to be measured, obtaining the zenith angle of the target to be measured, substituting the zenith angle of the target to be measured into the updated formula (4) for calculation, and obtaining the radiant illumination of the target to be measured under the current spectral channel; S17: replacing the first spectral channel with the second spectral channel of the high-speed rotating filter wheel 10, and repeating step S16 until the radiant illumination of the target to be measured under each spectral channel is obtained.

[0044] When the space target temperature inversion system obtains the spectral imaging of the target to be measured, the non-uniformity correction technology is first performed on the infrared detector 11 to correct the non-uniformity between the pixels of the infrared detector 11, and realize the non-uniformity correction of the photon level between each pixel of the infrared detector 11. Then, based on Planck's law, the calculated pixel spectral temperature difference is used as the system evaluation factor J to optimize the material emissivity until the temperature difference is stabilized to the convergence of the space target temperature inversion system.

[0045] S2: Based on the radiant illumination in each spectral channel, a functional relationship between the material emissivity and the surface temperature of the target surface element in each spectral channel is constructed; S21: Calculate the radiation solid angle Ω corresponding to a single pixel of the infrared detector 11: (5); in, is the area of ​​a single pixel of the focal plane array of the infrared detector 11, is the angle between the main optical line of the radiation and the main optical axis, is the focal length of the space target temperature inversion system; S22: Based on the mapping relationship between the face element of the target to be detected and the pixel of the infrared detector 11, set , combined with formula (5), the radiation brightness of the target to be measured in the detection direction is obtained: (6); in, is the radiation brightness L obtained by the i-th pixel incident on the i-th pixel of the infrared detector 11 through the spectral channel with a central wavelength of λ, is the radiant illumination obtained by the i-th pixel of the infrared detector 11 through the spectral channel with a central wavelength of λ; The image of the space target in the focal plane of the infrared detector 11 can be regarded as composed of a number of pixels with different temperatures. The infrared spectral radiation of the pixel is determined by the surface temperature of the pixel, the central wavelength of the narrow-band filter and the emissivity of the material.

[0046] S23: Apply formula (6) to obtain the radiant brightness Substituting into Planck's law, we can obtain the functional relationship between the material emissivity and surface temperature of the target surface element: (7); in, is the material emissivity of the i-th surface element included in the target surface element, is the first radiation constant, which is 3.742×10 -16 W·m 2 , is the second radiation constant, which is 1.4388×10 -2 m·K, is the surface temperature of the i-th element in the spectral channel with the central wavelength λ.

[0047] S3: Based on the functional relationship of step S2, a blind optimization algorithm is used to solve the radiation brightness under each spectral channel to obtain the temperature inversion result of the target to be measured.

[0048] S31: Set initial material emissivity and a fixed gain coefficient γ, assuming the initial material emissivity under each spectral channel same; S32: Initial material emissivity Substituting into equation (7), we can obtain the surface temperature of each facet under each spectral channel; S33: Take the average of the surface temperatures of all the facets and calculate the performance evaluation index using the following formula: (8); Among them, J i is the performance evaluation index of the i-th facet, is the central wavelength of the narrowband filter, m is the total number of narrowband filters, is the i-th element at the central wavelength The surface temperature calculated under the spectral channel is i is the average temperature of the i-th element calculated under each narrowband filter; S34: Generate random perturbation material emission rate in the interval [0, 1] that conforms to the Bernoulli distribution , using the first emission value Replace the initial material emissivity in step S32 , repeat steps S32-S33 to obtain the first performance evaluation index; use the second emission value Replace the initial material emissivity in step S32 , repeat steps S32-S33 to obtain a second performance evaluation index; take the difference between the first performance evaluation index and the second performance evaluation index as the evaluation coefficient N; S35: If ( <1), the surface temperature of each facet corresponding to each spectral channel is obtained to complete the temperature inversion of the target to be measured, otherwise the initial material emissivity of step S32 is replaced by the next material emissivity, and steps S32-S34 are repeated until So far, the surface temperature of each facet corresponding to each spectral channel is obtained, and the temperature inversion of the target to be measured is completed.

[0049] Emissivity of the j+1th material The calculation formula is: (9); in, is the iteration step length, is the difference between the evaluation factors of the first emission value and the second emission value, The material emissivity difference between the first emissivity value and the second emissivity value.

[0050] Assume that the target to be measured is a black body with a temperature of 323K and a real material emissivity of 0.76. Set the height filter wheel to have eight spectral channels, one of which is 8-12um full-pass and the remaining seven are narrowband. After calculation, the radiation brightness corresponding to the eight spectral channels is L=L1, L2, ... L8. Figure 4 As shown, the horizontal axis represents the preset material emissivity of the target, the vertical axis represents the temperature calculated by the preset material emissivity, and different colors represent different wavelengths. The temperature of each spectral channel is calculated by formula (7): The results show that when the preset material emissivity is lower than the real material emissivity, the radiation brightness inversion temperature of the larger wavelength is higher than that of the smaller wavelength; when the preset material emissivity is higher than the real material emissivity, the radiation brightness inversion temperature of the larger wavelength is lower than that of the smaller wavelength; when the preset material emissivity is close to the real material emissivity, the inversion temperatures of each wavelength are close and the temperature standard deviation is the smallest.

[0051] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0052] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A space target temperature inversion system for strong skylight background, characterized by: The invention comprises a telescope optical module, a cold optical infrared spectrum module, an infrared detector and a data processing module. The telescope optical module collects the optical signal of the target to be measured, and the optical signal is incident on the infrared detector for imaging via the cold optical infrared spectrum module to obtain a multi-band infrared image of the target. The infrared detector also sends the target infrared image to the data processing module. The data processing module uses an infrared standard star to perform infrared calibration on the target to be measured, and uses a blind optimization algorithm to process the infrared calibration result to realize the temperature inversion of the target to be measured.

2. The space target temperature inversion system for strong skylight background according to claim 1 is characterized by: The cold optical infrared spectrum module includes a low-temperature Dewar, and a long-wave attenuation plate, a first long-wave lens assembly, a second long-wave lens assembly and a high-speed rotating filter wheel placed inside the low-temperature Dewar. The light signal incident on the low-temperature Dewar is incident on the infrared detector via the long-wave attenuation plate, the first long-wave lens assembly, the second long-wave lens assembly and the high-speed rotating filter wheel in sequence.

3. The space target temperature inversion system for strong skylight background according to claim 2 is characterized by: The first long-wave lens assembly and the second long-wave lens assembly have the same structure, both comprising a translation stage and an optical element for secondary imaging, wherein the optical element is placed on the translation stage, and the translation stage drives the optical element to move relative to the telescope optical module.

4. The space target temperature inversion system for strong skylight background according to claim 2 is characterized by: The long-wave attenuation plate transmits a light beam of 8-12 microns; the high-speed rotating filter wheel includes a plurality of narrow-band filters, each of which corresponds to a spectral channel of a wavelength band.

5. A method for inverting the temperature of a space target facing a strong skylight background, which is implemented by using the space target temperature inversion system facing a strong skylight background as described in any one of claims 1 to 4, wherein the space target temperature inversion system comprises a high-speed rotating filter wheel, characterized in that: The specific steps include: S1: Based on the atmospheric extinction model, the infrared radiation response rate and atmospheric extinction coefficient of the space target temperature inversion system are obtained, and the radiant illumination of the target to be measured under each spectral channel of the high-speed rotating filter wheel is calculated based on the infrared radiation response rate and the atmospheric extinction coefficient; S2: Based on the radiant illumination in each spectral channel, a functional relationship between the material emissivity and the surface temperature of the target surface element in each spectral channel is constructed; S3: Based on the functional relationship of step S2, a blind optimization algorithm is used to solve the radiation brightness under each spectral channel to obtain the temperature inversion result of the target to be measured.

6. The method for inverting the temperature of a space target under a strong skylight background according to claim 5 is characterized in that: The step S1 specifically includes the following steps: S11: Based on the atmospheric extinction model, invert the radiance of the infrared standard star: （1）； （2）； （3）； in, is the pixel response value of the infrared detector after removing the atmospheric background, is the pixel bias of the infrared detector, is the irradiance of the target to be measured, is the response rate of the infrared detector pixel to the radiation illumination, is the atmospheric transmittance of the target to be measured at the zenith angle θ, is the atmospheric transmittance factor, is the atmospheric extinction model, is the atmospheric extinction optical thickness in the vertical direction, For air quality, is the zenith angle in degrees, λ is the central wavelength of the current spectral channel, is the target light intensity of the target to be measured; S12: Take the logarithm of equation (1): （4）； S13: Use the least squares method to fit equation (4) to obtain the atmospheric extinction coefficient and infrared radiation response rate , based on the atmospheric extinction coefficient and infrared radiation response rate Update formula (4); S14: adjusting the high-speed rotating filter wheel to the first spectral channel, measuring the target to be measured using the space target temperature inversion system, obtaining the zenith angle of the target to be measured, substituting the zenith angle of the target to be measured into the updated formula (4) for calculation, and obtaining the radiant illumination of the target to be measured under the current spectral channel; S15: replacing the first spectral channel with the second spectral channel of the high-speed rotating filter wheel, and repeating step S14 until the radiant illumination of the target to be measured under each spectral channel is obtained.

7. The method for inverting the temperature of a space target under a strong skylight background according to claim 5, characterized in that: Step S2 specifically includes the following steps: S21: Calculate the radiation solid angle Ω corresponding to a single pixel of the infrared detector: （5）； in, is the area of ​​a single pixel in the focal plane array of the infrared detector, is the angle between the main optical line of the radiation and the main optical axis, is the focal length of the space target temperature inversion system; S22: Based on the mapping relationship between the face element of the target to be measured and the pixel of the infrared detector, set , combined with formula (5), the radiation brightness of the target to be measured in the detection direction is obtained: （6）； in, is the radiant brightness obtained by the ith pixel of the infrared detector incident on the ith pixel through the spectral channel with a central wavelength of λ, is the radiant illumination obtained by the i-th pixel of the infrared detector incident on the i-th pixel through the spectral channel with a central wavelength of λ; S23: Apply formula (6) to obtain the radiant brightness Substituting into Planck's law, we can obtain the functional relationship between the material emissivity and surface temperature of the target surface element: （7）； in, is the material emissivity of the i-th surface element included in the target surface element, is the first radiation constant, which is 3.742×10 -16 W·m 2 , is the second radiation constant, which is 1.4388×10 -2 m·K, is the surface temperature of the i-th element in the spectral channel with the central wavelength λ.

8. The method for inverting the temperature of a space target under a strong skylight background according to claim 6 is characterized in that: Step S3 specifically includes the following steps: S31: Set initial material emissivity and a fixed gain factor γ; S32: Set the initial material emissivity under each spectral channel Same as the initial material emissivity Substituting into equation (7), we can obtain the surface temperature of each facet under each spectral channel; S33: Take the average of the surface temperatures of all the facets and calculate the performance evaluation index using the following formula: （8）； Among them, J i is the performance evaluation index of the i-th facet, is the central wavelength of the narrowband filter, m is the total number of narrowband filters, is the i-th element at the central wavelength The surface temperature calculated under the spectral channel is i is the average temperature of the i-th element calculated under each narrowband filter; S34: Generate random perturbation material emission rate in the interval [0, 1] that conforms to the Bernoulli distribution , using the first emission value Replace the initial material emissivity in step S32 , repeat steps S32-S33 to obtain the first performance evaluation index; use the second emission value Replace the initial material emissivity in step S32 , repeat steps S32-S33 to obtain a second performance evaluation index; take the difference between the first performance evaluation index and the second performance evaluation index as the evaluation coefficient N; S35: If , then the surface temperature of each facet corresponding to each spectral channel is obtained, and the temperature inversion of the target to be measured is completed. Otherwise, the initial material emissivity of step S32 is replaced by the next material emissivity, and steps S32-S34 are repeated until So far, the surface temperature of each facet corresponding to each spectral channel is obtained, and the temperature inversion of the target to be measured is completed.

9. The method for inverting the temperature of a space target under a strong skylight background according to claim 8, characterized in that: In step S35, the next material emissivity The calculation formula is: （9）； in, is the iteration step length, is the difference between the evaluation factors of the first emission value and the second emission value, The material emissivity difference between the first emissivity value and the second emissivity value.

10. The method for inverting the temperature of a space target under a strong skylight background according to claim 8, characterized in that: In step S35, <1.

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