Spatial target temperature inversion system and method for strong skylight background

Abstract

The present 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 includes: S1: obtaining the infrared radiation response rate and atmospheric extinction coefficient of the space target temperature inversion system based on the atmospheric extinction model, and calculating the irradiance of the target to be measured under each spectral channel of the high-speed rotating filter wheel based on the infrared radiation response rate and atmospheric extinction coefficient; S2: constructing a functional relationship between the material emissivity and surface temperature of the target surface element under each spectral channel based on the irradiance under each spectral channel; S3: solving the radiance under each spectral channel by using a blind optimization algorithm based on the functional relationship in step S2 to obtain the temperature inversion result of the target to be measured. The present invention performs blind optimization on the spectral material emissivity of the material, realizes real-time detection of low-temperature space targets, and inversely calculates the temperature distribution of complex materials (materials with different emissivities).

Description

Technical Field

[0001] The present 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. Background Art

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

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

[0004] Traditional methods obtain the temperature of a space target through methods such as full-band temperature measurement, colorimetric temperature measurement, spectral measurement, and multi-band radiation temperature measurement, but are insufficient to meet the application requirements for inverting the temperature of a space target with low temperature, low signal-to-noise ratio, and complex materials.

[0005] With the rapid development of space science and technology and the sharp increase in the number of artificial celestial bodies in space, as of now, the number of on-orbit artificial satellites has exceeded more than 19,000. Analyzing and judging the on-orbit operating status of artificial satellites is of great significance. However, the temperature of a space target is relatively low (usually about 220 - 360K), the observation distance is far, its infrared radiation characteristic signal is weak, and the lack of prior information such as material emissivity seriously affects the accuracy of obtaining the surface temperature distribution of a space target and the heat generation characteristics of an internal power source.

[0006] Existing technologies such as full-band temperature measurement, colorimetric temperature measurement, spectral temperature measurement, and multi-band radiation temperature measurement are difficult to continuously obtain the temperature of a low-temperature space target under complex sky regions and the distribution map of the infrared radiation characteristic density region, and cannot meet the application requirements for component temperature early warning of 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 the emissivity of all-wavelength radiation materials, and integrates all the radiant energy in the detection direction to determine the temperature of the space target, and cannot obtain temperature and other information for a target with unknown spectral material emissivity.

[0008] Colorimetric thermometry obtains the target temperature through the ratio relationship between the radiance of multiple bands and the ratio relationship of energy between different bands theoretically. This method takes into account the continuity of the spectral emissivity of the material, reduces the error caused by the unknown true value in temperature inversion through the radiance ratio relationship between multiple bands, but also has higher requirements for the signal-to-noise ratio of space targets. Especially for low-temperature targets with radiance often lower than 1, the ratio relationship will introduce a large amount of noise, resulting in the annihilation of the temperature signal of space targets and unclear edges.

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

[0010] Multi-band radiation thermometry combines parameters such as path radiation, atmospheric attenuation, and system transmittance to formulate the material emissivity, and then inversely calculates the target temperature through the target radiance. However, multi-band temperature inversion is a ill-posed problem in mathematics, that is, the number of unknown parameters is more than the number of measurement equations. The unclear prior information of the material emissivity leads to inaccurate temperature measurement by this method. Summary of the Invention

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

[0012] To achieve the above object, the technical solution of the present invention is realized as follows:

[0013] A space target temperature inversion system for a strong skylight background includes a telescope optical module, a cold optical infrared spectroscopy module, an infrared detector, and a data processing module. The telescope optical module collects the optical signal of the target to be measured. The optical signal is incident on the infrared detector through the cold optical infrared spectroscopy module for imaging to obtain a multi-band target infrared image. 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.

[0014] Further, the cold optical infrared spectroscopy module includes a cryogenic dewar, and a long-wave attenuation sheet, a first long-wave lens assembly, a second long-wave lens assembly, and a high-speed rotating filter wheel disposed inside the cryogenic dewar. The optical signal incident on the cryogenic dewar is incident on the infrared detector through the long-wave attenuation sheet, the first long-wave lens assembly, the second long-wave lens assembly, and the high-speed rotating filter wheel in sequence.

[0015] Further, the first long-wave lens assembly and the second long-wave lens assembly have the same structure, and both include a displacement stage and an optical element for secondary imaging. The optical element is disposed on the displacement stage, and the displacement stage drives the optical element to displace relative to the telescope optical module.

[0016] Further, the long-wave attenuation sheet can transmit a beam of 8-12 microns; the high-speed rotating filter wheel includes a plurality of narrow-band filter sheets, and each narrow-band filter sheet corresponds to a spectral channel of a certain band.

[0017] A method for inverting the temperature of a space target facing a strong skylight background is realized by using a space target temperature inversion system facing a strong skylight background. The space target temperature inversion system includes a high-speed rotating filter wheel, and specifically includes the following steps:

[0018] 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 irradiance of the target to be measured under each spectral channel of the high-speed rotating filter wheel based on the infrared radiation response rate and the atmospheric extinction coefficient;

[0019] S2: Based on the irradiance under each spectral channel, construct a functional relationship between the material emissivity and the surface temperature of the target surface element under each spectral channel;

[0020] S3: Based on the functional relationship in step S2, use a blind optimization algorithm to solve the radiance under each spectral channel to obtain the temperature inversion result of the target to be measured.

[0021] Further, step S1 specifically includes the following steps:

[0022] S11: Invert the irradiance of the infrared standard star based on the atmospheric extinction model:

[0023] (1);

[0024] (2);

[0025] (3);

[0026] Wherein, is the pixel response numerical quantity of the infrared detector after removing the atmospheric background, is the pixel offset of the infrared detector, is the irradiance of the target to be measured, is the responsivity of the pixel of the infrared detector to the irradiance, 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, is the air mass, is the zenith angle in degrees, λ is the central wavelength of the current spectral channel, is the target luminous intensity of the target to be measured;

[0027] S12: Take the logarithm of Equation (1):

[0028] (4);

[0029] S13: Use the least squares method to fit Equation (4) to obtain the atmospheric extinction coefficient and the infrared radiation responsivity , and update Equation (4) based on the atmospheric extinction coefficient and the infrared radiation responsivity ;

[0030] S14: Adjust the high-speed rotating filter wheel to the first spectral channel, measure the target to be measured using the space target temperature inversion system to obtain the zenith angle of the target to be measured, and substitute the zenith angle of the target to be measured into the updated Equation (4) for calculation to obtain the irradiance of the target to be measured under the current spectral channel;

[0031] S15: Replace the first spectral channel with the second spectral channel of the high-speed rotating filter wheel, and repeat step S14 until the irradiance of the target to be measured under each spectral channel is obtained.

[0032] Further, step S2 specifically includes the following steps:

[0033] S21: Calculate the radiation solid angle Ω corresponding to a single pixel of the infrared detector:

[0034] (5);

[0035] Wherein, is the area of a single pixel of 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;

[0036] S22: Based on the mapping relationship between the surface element of the target to be measured and the pixel of the infrared detector, set , the radiance of the target to be measured in the detection direction is obtained by combining formula (5):

[0037] (6);

[0038] Among them, is the radiance L obtained when the i-th surface element is incident on the i-th pixel of the infrared detector through the spectral channel with the central wavelength of λ, is the irradiance obtained when the i-th surface element is incident on the i-th pixel of the infrared detector through the spectral channel with the central wavelength of λ;

[0039] S23: Substitute the radiance obtained by formula (6) into Planck's law to obtain the functional relationship between the material emissivity and the surface temperature of the target surface element:

[0040] (7);

[0041] Among them, is the material emissivity of the i-th surface element included in the target surface element, is the first radiation constant, taking 3.742×10 -16 W·m 2 , is the second radiation constant, taking 1.4388×10 -2 m·K, is the surface temperature of the i-th surface element under the spectral channel with the central wavelength of λ.

[0042] Further, step S3 specifically includes the following steps:

[0043] S31: Set the initial material emissivity and the fixed gain coefficient γ;

[0044] S32: Assume that the initial material emissivities under each spectral channel are the same, and substitute the initial material emissivity into formula (7) to obtain the surface temperatures of each surface element under each spectral channel;

[0045] S33: Take the average value of the surface temperatures of all surface elements and calculate the performance evaluation index through the following formula:

[0046] (8);

[0047] Among them, J i is the performance evaluation index of the i-th surface element, is the central wavelength of the narrowband filter, m is the total number of narrowband filters, is the surface temperature calculated for the i-th surface element under the spectral channel with the central wavelength of ​ i is the average temperature of the i-th bin calculated under each narrowband filter;

[0048] 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;

[0049] 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 bin corresponding to each spectral channel is obtained, and the temperature inversion of the target to be measured is completed.

[0050] Furthermore, in step S35, the next material emissivity The calculation formula is:

[0051] (9);

[0052] in, is the iteration step length, is the difference in evaluation factors between the first emission value and the second emission value, The difference in material emissivity between the first emissivity value and the second emissivity value.

[0053] Furthermore, in step S35, <1.

[0054] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0055] (1) The present invention creates a temperature inversion system and method for space targets facing a strong skylight background, which 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.

[0056] (2) The temperature inversion system and method for space targets facing strong skylight background of the present invention adopt a temperature inversion system for space targets (a cold optical infrared detection system composed of a cryogenic dewar, a long-wave attenuation sheet, a first long-wave lens assembly, a second long-wave lens assembly, a high-speed rotating filter wheel, and an infrared detector), reducing the background infrared radiation noise and achieving multi-spectral and high-resolution infrared imaging of low-temperature space targets.

[0057] (3) The temperature inversion system and method for space targets facing strong skylight background of the present invention adopt a blind optimization algorithm to blindly optimize and correct the spectral emissivity of materials, reducing the influence of unknown material emissivity on the inversion accuracy of the equivalent temperature of different components and achieving the acquisition of the temperature distribution of complex materials of low-temperature targets.

[0058] (4) The temperature inversion system and method for space targets facing strong skylight background of the present invention use a temperature inversion system for space targets (a cold optical infrared detection system) to image the radiation characteristics of space targets. By utilizing the difference caused by the influence of the deviation of the material emissivity on the infrared multi-band radiance, combined with a blind optimization algorithm (such as the stochastic parallel gradient descent algorithm), the spectral emissivity of materials is blindly optimized and corrected, thereby improving the accuracy of the inversion temperature of different components (with different material emissivities) of space targets. Compared with traditional methods, the present invention neither requires the known material emissivity as prior information nor requires high requirements for the signal-to-noise ratio of the target. By utilizing the continuity of the emissivity of adjacent spectral materials and the true error of the spectral emissivity to reduce the difference brought by the multi-band spectral radiance, combined with a blind optimization algorithm to optimize and correct the material emissivity at the pixel level, information such as the temperature distribution on the target surface and the heat generation characteristics of internal power sources is obtained, which is expected to greatly improve the temperature inversion fineness and accuracy of infrared detectors and achieve temperature early warning for space target components. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0060] Figure 1 is a schematic structural diagram of the temperature inversion system for space targets facing strong skylight background according to an embodiment of the present invention;

[0061] Figure 2 is a schematic flow diagram of the temperature inversion method for space targets facing strong skylight background according to an embodiment of the present invention;

[0062] Figure 3 is a schematic structural diagram of the monochromator scanning calibration according to an embodiment of the present invention;

[0063] Figure 4 It is the deviation curve between the preset material emissivity of the space target described in the embodiment of the present invention and the target temperature retrieved by each spectral channel.

[0064] Explanation of reference numerals:

[0065] 1. Primary mirror; 2. Secondary mirror; 3. Secondary mirror light shield; 4. Primary mirror barrel light shield ring; 5. Primary mirror light shield tube; 6. Cryogenic dewar; 7. Long-wave attenuation sheet; 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 carbide rod; 14. Entrance slit; 15. Collimator; 16. Grating; 17. Focusing mirror; 18. Exit slit; 19. Collimator tube. Detailed implementation manners

[0066] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention.

[0067] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0068] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is 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 to 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 the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0069] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0070] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments.

[0071] As Figure 1 shown, the spatial target temperature inversion system for strong skylight background proposed by the present invention includes a telescope optical module, a cold optical infrared spectral 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. The optical signal is incident on the infrared detector 11 through the cold optical infrared spectral module for imaging, obtaining the target infrared image in multiple bands. 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 the stochastic parallel gradient descent algorithm (SPGD algorithm), genetic algorithm, differential algorithm, and annealing algorithm) to process the infrared calibration result, realizing the temperature inversion of the target to be measured.

[0072] The detailed structure of the above modules will be introduced below. The telescope optical module includes a primary mirror 1, a secondary mirror 2, a secondary mirror light shield, a primary mirror barrel light shield ring, and a primary mirror light shield tube. The incident light passes through the primary mirror 1 and is incident on the secondary mirror 2. The light reflected by the secondary mirror 2 is incident on the cold optical infrared spectral module through the primary mirror 1. The primary mirror 1 and the secondary mirror 2 adopt a Cassegrain structure. A primary mirror barrel light shield ring is provided on the primary mirror 1. The secondary mirror 2 is placed inside the primary mirror barrel light shield ring. The inner wall of the barrel of the primary mirror 1 extends outward and exceeds the secondary mirror 2. Multiple layers of light shield rings are provided on the inner wall of the barrel to form the primary mirror barrel light shield ring, reducing the influence of off-axis stray light. A primary mirror light shield tube is also provided on the primary mirror 1. The primary mirror light shield tube is located between the primary mirror 1 and the secondary mirror 2, and is used to suppress the stray light other than the light beam transmitted between the primary mirror 1 and the secondary mirror 2. A secondary mirror light shield is provided on the secondary mirror 2. The combination of the secondary mirror light shield, the primary mirror barrel light shield ring, and the primary mirror light shield tube suppresses the stray light, reducing the influence of the stray light on the subsequent image processing. The telescope optical module is mainly responsible for the signal acquisition, transmission of the spatial target, and the suppression of off-axis stray light. The signal of the spatial target is reflected by the primary and secondary mirrors 2 and sent to the subsequent cold optical infrared detection system (including the cold optical infrared spectral module, the infrared detector 11, and the data processing module 12) for processing.

[0073] The cold optical infrared spectral module includes a cryogenic dewar 6, and a long-wave attenuation sheet 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 cryogenic dewar 6. The optical signal incident on the cryogenic dewar 6 is incident on the infrared detector 11 successively through the long-wave attenuation sheet 7, the first long-wave lens assembly 8, the second long-wave lens assembly 9, and the high-speed rotating filter wheel 10. The cryogenic dewar 6 is equipped with a vacuum valve interface and is connected to a molecular pump through a KF flange to make the vacuum degree in the cavity reach 10 - 3 Pa. Two 15W@77K (-196°C) gas-bearing Stirling cryocoolers are used to stabilize the temperature in the cavity at 120K, reduce the 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 sheet 7 inside the cryogenic dewar 6. The long-wave attenuation sheet 7 can transmit light beams with wavelengths of 8-12 microns. 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 optical lens with material emissivity is placed on the displacement stage with material emissivity. The displacement stage drives the optical lens to displace relative to the telescope optical module. The first long-wave lens assembly 8 and the second long-wave lens assembly 9 have the ability to adjust one-dimensional degrees of freedom, which is used to compensate for the defocus caused by temperature changes during the imaging process of the telescope optical module. The high-speed rotating filter wheel 10 mainly consists of a servo motor, a motor base, a coupling, a magnetic fluid, a filter wheel, etc. The filter wheel includes multiple filter films. Each filter film transmits light of one wavelength band, that is, corresponding to one spectral channel of one wavelength band. Each filter film can transmit light of different wavelength bands, so that the infrared detector 11 can quickly switch the filter films during the high-frequency exposure process to obtain multi-band target infrared images. After the light beam is attenuated, it passes through the imaging lens group inside the cryogenic dewar 6 and hits the camera target surface of the infrared detector 11, realizing the unknown matching between the primary mirror 1 and the camera cold stop. By rotating the filter films of the filter wheel and synchronously exposing them with the corresponding infrared detector 11, the multi-spectral imaging in the infrared band of the space target is completed.

[0074] The data processing module 12 is used to implement the functions of infrared calibration and temperature inversion. First, the infrared radiation of the target to be measured is calibrated in real time by an infrared standard star to obtain the infrared radiation responsivity and the atmospheric extinction coefficient of the space target temperature inversion system, so as to improve the measurement accuracy of the infrared irradiance of the space target. Then, a long-wave cooled infrared detector 11 is used to detect the space target to obtain the measured multi-band target infrared image. The emissivity of the material is determined, the radiance of each pixel of the infrared detector 11 is calculated, and the temperature difference of the multi-band inversion is used as the evaluation factor of the space target temperature inversion system. Combined with a blind optimization algorithm (stochastic parallel gradient descent algorithm), the emissivity of the material is blindly optimized to make the multi-band temperature standard deviation stable and less than 5K, reduce the influence of the unclear prior information of the material emissivity on temperature measurement, complete the system convergence, and thus invert the temperature distribution map of the space target with complex materials (different material emissivities), low temperature and low signal-to-noise ratio.

[0075] As Figure 2 shown, the space target temperature inversion method for a strong skylight background provided by the present invention is implemented by a space target temperature inversion system for a strong skylight background, and specifically includes the following steps:

[0076] S1: Obtain the infrared radiation responsivity and the atmospheric extinction coefficient of the space target temperature inversion system based on the atmospheric extinction model, and calculate the irradiance of the target to be measured under each spectral channel of the high-speed rotating filter wheel 10 based on the infrared radiation responsivity and the atmospheric extinction coefficient.

[0077] Infrared calibration includes spectral calibration and radiation calibration, and its purpose is to determine the central wavelength of each spectral channel and the response at different wavelengths respectively, and establish a quantitative relationship between the irradiance of the incident radiation of the target to be measured and the pixel gray response value of the target infrared image.

[0078] S11: Calibrate the central wavelength, spectral response range and wavelength response curve of each spectral channel of the high-speed filter wheel by using the monochromator scanning calibration method to achieve spectral calibration.

[0079] As Figure 3As shown in the figure, the structure of the monochromator mainly includes an incident slit 14, a collimating mirror 15, a grating 16, a focusing mirror 17, and an exit slit 18. During the calibration process, first, set the scanning wavelength range of the monochromator, the width of the incident slit 14, and the width of the exit slit 18 through the monochromator control software. The light emitted by the silicon carbide rod 13 is evenly irradiated on the incident slit 14 of the monochromator, adjusted to parallel light by the collimating mirror 15, and after being reflected by the grating 16, it generates multi-order diffracted monochromatic parallel light, which reaches the position of the exit slit 18 through the focusing mirror 17. The light emerging from the slit is adjusted to parallel light by the off-axis parabolic mirror of the collimator 19, and after signal modulation, it enters the cold optical infrared spectral module, the infrared detector 11, and the data processing module 12 in sequence. Adjust the high-speed rotating filter wheel 10 so that the light emitted by the monochromator can irradiate on each spectral channel, record the wavelength and pixel gray-scale response values of the response of the infrared detector during the scanning process of the monochromator, and draw the wavelength response curve; fit the wavelength response curve through the Gaussian function to determine the central wavelength and spectral response range of each spectral channel of the high-speed filter wheel.

[0080] Next, perform radiometric calibration:

[0081] 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 use the space target temperature inversion system to calibrate the selected infrared standard stars;

[0082] After completing the work of S11 - S12, the radiometric calibration results will be more accurate.

[0083] S13: Based on the atmospheric extinction model, invert the irradiance of the infrared standard star:

[0084] (1);

[0085] (2);

[0086] (3);

[0087] Among them, is the pixel response numerical quantity of the infrared detector 11 after removing the atmospheric background, is the pixel offset 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 irradiance, 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 vertical atmospheric extinction optical thickness, is the air mass, 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;

[0088] S14: Take the logarithm of Equation (1):

[0089] (4);

[0090] When the zenith distance < 75°, the atmosphere can be approximately regarded as a plane parallel layer, and the calculation formula of the air mass is , otherwise the value remains unchanged.

[0091] S15: Use the least squares method to fit Equation (4) to obtain the atmospheric extinction coefficient and the infrared radiation responsivity , and update Equation (4) based on the atmospheric extinction coefficient and the infrared radiation responsivity ;

[0092] S16: Adjust the high-speed rotating filter wheel 10 to the first spectral channel, measure the target to be measured using the space target temperature inversion system, obtain the zenith angle of the target to be measured, and substitute the zenith angle of the target to be measured into the updated Equation (4) for calculation to obtain the irradiance of the target to be measured in the current spectral channel;

[0093] S17: Replace the first spectral channel with the second spectral channel of the high-speed rotating filter wheel 10, and repeat step S16 until the irradiance of the target to be measured in each spectral channel is obtained.

[0094] When the space target temperature inversion system acquires the spectral imaging of the target to be measured, first perform non-uniform correction technology on the infrared detector 11 to correct the non-uniformity between the pixels of the infrared detector 11, and achieve the correction of the photon-level non-uniformity between the pixels of the infrared detector 11. Then, based on Planck's law, use the calculated pixel spectral temperature difference as the system evaluation factor J to optimize the material emissivity until the temperature difference stabilizes and the space target temperature inversion system converges.

[0095] S2: Based on the irradiance in each spectral channel, construct a functional relationship between the material emissivity and the surface temperature of the target surface element in each spectral channel;

[0096] S21: Calculate the radiation solid angle Ω corresponding to a single pixel of the infrared detector 11:

[0097] (5);

[0098] Among them, 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 radiation and the main optical axis, is the focal length of the spatial target temperature inversion system;

[0099] S22: Based on the mapping relationship between the surface elements of the target to be measured and the pixels of the infrared detector 11, set , and combine formula (5) to obtain the radiance of the target to be measured in the detection direction:

[0100] (6);

[0101] Among them, is the radiance L obtained when the i-th surface element is incident on the i-th pixel of the infrared detector 11 through the spectral channel with the central wavelength of λ, is the irradiance obtained when the i-th surface element is incident on the i-th pixel of the infrared detector 11 through the spectral channel with the central wavelength of λ;

[0102] The image formed by the spatial target on the focal plane of the infrared detector 11 can be regarded as composed of several pixels with different temperatures. The infrared spectral radiation of the pixels is determined by the surface temperature of the surface element, the central wavelength of the narrow-band filter, and the material emissivity.

[0103] S23: Substitute the radiance obtained by formula (6) into Planck's law to obtain the functional relationship between the material emissivity and the surface temperature of the target surface element:

[0104] (7);

[0105] Among them, is the material emissivity of the i-th surface element included in the target surface element, is the first radiation constant, taking 3.742×10 -16 W·m 2 , is the second radiation constant, taking 1.4388×10 -2 m·K, is the surface temperature of the i-th surface element under the spectral channel with the central wavelength of λ.

[0106] S3: Based on the functional relationship in step S2, use the blind optimization algorithm to solve the radiance under each spectral channel to obtain the temperature inversion result of the target to be measured.

[0107] S31: Set the initial material emissivity and the fixed gain coefficient γ, and assume that the initial material emissivities under each spectral channel are the same;

[0108] S32: Substitute the initial material emissivity into Equation (7) to obtain the surface temperature of each surface element under each spectral channel;

[0109] S33: Take the average value of the surface temperatures of all surface elements and calculate the performance evaluation index through the following formula:

[0110] (8);

[0111] where, J i is the performance evaluation index of the i-th surface element, is the central wavelength of the narrowband filter, m is the total number of narrowband filters, is the surface temperature calculated for the i-th surface element under the spectral channel with the central wavelength of , i is the average temperature calculated for the i-th surface element under each narrowband filter;

[0112] S34: Generate a random perturbation material emissivity that conforms to the Bernoulli distribution in the interval [0, 1], and use the first emission value to replace the initial material emissivity in step S32 , repeat steps S32 - S33 to obtain the first performance evaluation index; use the second emission value to replace the initial material emissivity in step S32 , repeat steps S32 - S33 to obtain the second performance evaluation index; take the difference between the first performance evaluation index and the second performance evaluation index as the evaluation coefficient N;

[0113] S35: If ( < 1), then obtain the surface temperature of each surface element corresponding to each spectral channel, complete the temperature inversion of the target to be measured, otherwise use the next material emissivity to replace the initial material emissivity in step S32, repeat steps S32 - S34 until is reached, obtain the surface temperature of each surface element corresponding to each spectral channel, and complete the temperature inversion of the target to be measured.

[0114] The calculation formula for the (j + 1)-th material emissivity is:

[0115] (9);

[0116] where, is the iteration step size, is the difference in the evaluation factors between the first emission value and the second emission value, is the difference in material emissivity between the first emission value and the second emission value.

[0117] Assume that the target to be measured is a blackbody with a temperature of 323K and a true material emissivity of 0.76. It is set that the height filter wheel has eight spectral channels, one of which is a full pass of 8 - 12um, and the remaining seven spectral channels are narrowband. After calculation, the radiance L corresponding to the eight spectral channels is L = L1, L2, …… L8. As Figure 4 shown, the abscissa represents the preset material emissivity of the target, the ordinate represents the temperature calculated through the preset material emissivity, and different colors represent different wavelengths. Calculate the temperature of each spectral channel through formula (7) . The results show that when the preset material emissivity is lower than the true material emissivity, the temperature inverted from the radiance with a larger wavelength is higher than that with a smaller wavelength; when the preset material emissivity is higher than the true material emissivity, the temperature inverted from the radiance with a larger wavelength is lower than that with a smaller wavelength; when the preset material emissivity is close to the true material emissivity, the inverted temperatures of each wavelength are close and the temperature standard deviation is the smallest.

[0118] It should be understood that various forms of the processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in the disclosure of the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and no limitations are imposed herein.

[0119] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub - combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for temperature inversion of a space target facing a strong skylight background, which is implemented by a temperature inversion system of a space target facing a strong skylight background. The temperature inversion system of the space target includes a high-speed rotating filter wheel, and also includes a telescope optical module, a cold optical infrared spectroscopy module, an infrared detector, and a data processing module. The telescope optical module collects the optical signal of the target to be measured. The optical signal is incident on the infrared detector through the cold optical infrared spectroscopy module for imaging to obtain a multi-band target infrared image. The infrared detector also sends the target infrared image to the data processing module. The data processing module performs infrared calibration on the target to be measured using an infrared standard star, and processes the infrared calibration result using a blind optimization algorithm to achieve temperature inversion of the target to be measured; characterized in that: The method for temperature inversion of space targets facing strong skylight background specifically includes the following steps: S1: Obtain the infrared radiation response rate and atmospheric extinction coefficient of the space target temperature inversion system based on the atmospheric extinction model, and calculate the irradiance of the target to be measured under each spectral channel of the high-speed rotating filter wheel based on the infrared radiation response rate and atmospheric extinction coefficient; S2: Based on the irradiance under each spectral channel, construct a functional relationship between the material emissivity and surface temperature of the target surface element under each spectral channel; S3: Based on the functional relationship in step S2, use a blind optimization algorithm to solve the radiance under each spectral channel to obtain the temperature inversion result of the target to be measured.

2. The method for inverting the temperature of a space target facing a strong skylight background according to claim 1, wherein: The cold optical infrared spectral module includes a cryogenic dewar, and a long-wave attenuation sheet, a first long-wave lens assembly, a second long-wave lens assembly, and a high-speed rotating filter wheel placed inside the cryogenic dewar. The optical signal incident on the cryogenic dewar is incident on the infrared detector through the long-wave attenuation sheet, the first long-wave lens assembly, the second long-wave lens assembly, and the high-speed rotating filter wheel in sequence.

3. The temperature inversion method for space targets facing strong skylight background according to claim 2, characterized in that: The structures of the first long-wave lens assembly and the second long-wave lens assembly are the same, and both include a displacement stage and an optical element for secondary imaging. The optical element is placed on the displacement stage, and the displacement stage drives the optical element to displace relative to the telescope optical module.

4. The method for inverting the temperature of a space target facing a strong skylight background according to claim 2, wherein: The long-wave attenuation sheet transmits light beams with wavelengths of 8 - 12 microns; the high-speed rotating filter wheel includes a plurality of narrow-band filter sheets, and each narrow-band filter sheet corresponds to a spectral channel of a certain band.

5. The method for inverting the temperature of a space target facing a strong skylight background according to claim 1, wherein: The specific steps of step S1 are as follows: S11: Invert the irradiance of the infrared standard star based on the atmospheric extinction model; （1）； （2）； （3）； Among them, is the pixel response numerical quantity of the infrared detector after removing the atmospheric background, is the pixel offset of the infrared detector, is the irradiance of the target to be measured, is the responsivity of the pixel of the infrared detector to the irradiance, 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, is the air mass, is the zenith angle in degrees, λ is the central wavelength of the current spectral channel, is the target luminous 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 the infrared radiation responsivity , and update Equation (4) based on the atmospheric extinction coefficient and the infrared radiation responsivity ; S14: Adjust the high-speed rotating filter wheel to the first spectral channel, measure the target to be measured using the space target temperature inversion system to obtain the zenith angle of the target to be measured, and substitute the zenith angle of the target to be measured into the updated equation (4) for calculation to obtain the irradiance of the target to be measured under the current spectral channel; S15: Replace the first spectral channel with the second spectral channel of the high-speed rotating filter wheel, and repeat step S14 until the irradiance of the target to be measured under each spectral channel is obtained.

6. The temperature inversion method for space targets facing strong skylight background according to claim 1, characterized in that: The specific steps of step S2 are as follows: S21: Calculate the radiation solid angle Ω corresponding to a single pixel of the infrared detector; （5）； wherein, is the area of a single pixel of 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 spatial target temperature inversion system; S22: Based on the mapping relationship between the surface elements of the target to be measured and the pixels of the infrared detector, set , and combine with formula (5) to obtain the radiance of the target to be measured in the detection direction: （6）； Among them, is the radiance obtained when the i-th surface element is incident on the i-th pixel of the infrared detector through the spectral channel with the central wavelength of λ. is the irradiance obtained when the i-th surface element is incident on the i-th pixel of the infrared detector through the spectral channel with the central wavelength of λ. S23: Substitute the radiance obtained from formula (6) into Planck's law to obtain the functional relationship between the material emissivity and surface temperature of the target surface element: （7）； Among them, is the material emissivity of the i-th surface element included in the target surface element, is the first radiation constant, taking 3.742×10 -16 W·m 2 , is the second radiation constant, taking 1.4388×10 -2 m·K, is the surface temperature of the i-th surface element under the spectral channel with a central wavelength of λ.

7. The spatial target temperature inversion method for strong skylight background according to claim 5, characterized in that: The specific steps of step S3 are as follows: S31: Set the initial material emissivity and the fixed gain coefficient γ; S32: Set the initial material emissivity for each spectral channel to be the same, and substitute the initial material emissivity into Equation (7) to obtain the surface temperature of each surface element for each spectral channel; S33: Take the average of the surface temperatures of all surface elements, and calculate the performance evaluation index through the following formula: （8）； Among them, J i is the performance evaluation index of the i-th facet element, is the central wavelength of the narrowband filter, m is the total number of narrowband filters, is the surface temperature calculated for the i-th facet element in the spectral channel with a central wavelength of ; i is the average temperature calculated for the i-th facet element under each narrowband filter; S34: Generate a random perturbation material emissivity that conforms to the Bernoulli distribution in the interval [0, 1] , and replace the initial material emissivity in step S32 with the first emissivity value . Repeat steps S32 - S33 to obtain the first performance evaluation index; replace the initial material emissivity in step S32 with the second emissivity value . Repeat steps S32 - S33 to obtain the second performance evaluation index; take the difference between the first performance evaluation index and the second performance evaluation index as the evaluation coefficient N . Repeat steps S32 - S33 to obtain the second performance evaluation index; replace the initial material emissivity in step S32 with the second emissivity value . Repeat steps S32 - S33 to obtain the 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 , the surface temperature of each pixel corresponding to each spectral channel is obtained, and the temperature inversion of the target to be measured is completed. Otherwise, the initial material emissivity in step S32 is replaced with the next material emissivity, and steps S32 - S34 are repeated until is reached, the surface temperature of each pixel corresponding to each spectral channel is obtained, and the temperature inversion of the target to be measured is completed.

8. The method for temperature inversion of a space target facing a strong skylight background according to claim 7, characterized in that: In step S35, the calculation formula for the emissivity of the next material is as follows: （9）； wherein, is the iteration step size, is the evaluation factor difference between the first emission value and the second emission value, is the material emissivity difference between the first emission value and the second emission value.

9. The method for temperature inversion of a space target facing a strong skylight background according to claim 7, wherein: In step S35, <1.

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