| Infrared spectral remote sensing technology is an important means of remote sensing that emerged in the late 20th century,and China’s independent research and development of infrared remote sensors has been used in basic scientific research,national defense security and military-civilian integration such as meteorology,marine remote sensing,resource survey,environmental and ecological monitoring.The Noise Equivalent Spectral Radiance(NESR)of an infrared remote sensor is a key indicator of its limit detection capabilities.At present,China does not yet meet the NESR calibration equipment and verification specifications of high-precision,wide dynamic range,large aperture high-end remote sensors,and the research of engineered NESR measurement technology is of great scientific significance and application value for the development,application effect evaluation and continuous improvement of China’s military and civilian infrared remote sensors and the continuous improvement of technical level.The doctoral thesis of this project combined with the major research and development tasks of national defense equipment carried out the research on the development of NESR calibration system and performance test methods for infrared remote sensors.The research content of the paper mainly includes:1)the overall scheme design of NESR calibration method and calibration system,2)the design and process scheme of the calibration light source,3)the simulation of the mechanical and thermal properties of the calibration path,and 4)the NESR calibration experiment and uncertainty analysis.The paper investigates the NESR calibration method and calibration device at home and abroad,analyzes the technical characteristics of the two calibration schemes of electronics and optics,combines the radiation characteristics characterization requirements of infrared remote sensors,sorts out the technical requirements of NESR calibration,and designs the overall scheme of the calibration system composed of the calibration light source,the calibration path,the low-temperature vacuum unit and the measurement and control unit.This paper proposes and applies a cascading gold-plated integrating sphere calibration light source scheme with adjustable dynamic range,which provides a new technology to meet the contradictory design requirements of aperture expansion and high uniformity and high stability of the calibration light source.The output spectral radiance of the integrating sphere is traced back to the standard blackbody of the Chinese metrology institute,which ensures the measurement accuracy of NESR.The system design takes into account the testing needs of low temperature vacuum and normal temperature and pressure,and has better engineering applicability.In order to improve the luminous uniformity of the large-bore gold-plated integrating sphere and the stability of the vacuum low-temperature environment,the paper uses the vacuum evaporative gold plating process to increase the coating reflectivity from about 80%of the original chemical plating to more than 90%,improves the stability and firmness of the film layer in the low-temperature working environment,adopts a die-casting molding to ensure the sphericalness of the inner wall of the integrating sphere and the uniformity of the gold film,and uses the hightemperature silver copper welding process to improve the thermal conductivity of the outer wall cooling pipeline,reduces the non-uniformity of the background radiation of the spherical shell,and realizes the optical aperture of 250 The non-uniformity of the integrating spherical surface of mm is less than 0.3%,and the angular non-uniformity is less than 0.2%.The total optical path of the NESR calibration system is up to 2.33 m,and the optics are installed in a normal temperature and pressure environment,which is used in a vacuum low temperature environment with a vacuum degree of 10-3 Pa and a temperature of 193 K.In order to characterize the optical path changes introduced by the installation and adjustment of long-range optical paths and the differences in the use environment,the paper uses the finite element simulation software PATRAN to establish the force transmission link of the overall structure of the calibration chamber,and the temperature change characteristics of the optical components and optical paths are analyzed by using the multiphysics simulation software COMSOL,and the rationality of the simulation results is verified by experiments.Combining the simulation results and scheme comparison,the paper uses dual off-axis parabolic mirrors and rotary mirrors to realize the switching of three standard blackbody and integrating sphere test optical paths,and through continuous optimization of the design,a stable optical path support scheme based on the optical platform is proposed and implemented,and the optical path assembly test results of the dynamic interferometer show that the optical path wavefront error at room temperature and atmospheric pressure and vacuum is less than λ/6(RMS)and λ/5(RMS),respectively,under the condition of temperature change in the cabin of 138～353 K.The optical path wavefront error is still better than λ/4,which meets the design requirements of high stability of the optical path under low temperature vacuum,and provides a useful reference for the engineering design of the optical path for low temperature vacuum testing.Based on the NESR measurement equation of high-end infrared remote sensor,the influence of 11 uncertainties,such as the traceability of the absolute spectral spoke brightness,the uniformity and stability of the output of the integrating sphere,are analyzed and experimentally evaluated according to the NESR measurement equation.Experimental results show that in the specified bright temperature range of 303～308 K,the relative uncertainty of the radiance of the integrating sphere spectrum is better than 0.34%,and the uncertainty of the NESR calibration in the 6～15 μm band is better than that of 0.1～0.0037 μW·cm-2·sr-1·μm-1.The research results of the paper verify the engineering application feasibility of the new NESR calibration system,and provide direct technical support for improving the NESR testing capability of infrared remote sensors in China and further formulating the verification specifications. |
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