Research On Key Technologies Of Stray Light Measurement For Large Aperture Optical System

In order to meet the needs of the development of China's geology,surveying,and mapping,environment,resources,and space exploration,more and more remote sensing cameras with high sensitivity,high resolution,and high detection capability have come out and are required higher and higherfor stray light.Therefore,the stray light test has been re-raised to an important position,prompting people to invest a lot of manpower,material,and financial resources to restart the study of stray light test problems that were once neglected and directly affected the success or failure of the camera.The stray light test of camera is divided into stray light coefficient test and stray light suppression ratio test.The stray light suppression ratio is usually used to evaluate the stray light level of high sensitivity and large-caliber cameras.The stray light suppression ratio can be expressed by PST(Point Source Transmittance).This paper mainly studies the PST test technology of high sensitivity and large-caliber cameras,whose PST test ability is mainly measured.Method and limitation of calibration technology.In order to improve the ability of PST testing,firstly,the scattering characteristics of key surfaces affecting PST testing and calibration are analyzed,the relationship between stray light and material surface scattering properties is deduced theoretically,and a set of accurate scattering model attribute database is established,which provides design basis for accurate simulation analysis of stray light between testing system and calibration lens itself;secondly,the large-caliber is studied.Starting from the key technology of improving the PST test capability of the system,the influence of high brightness uniform target simulation technology,high efficiency stray light suppression technology and PST test accuracy calibration technology on the test capability is analyzed.A large-caliber and high-precision PST test system is established.Its measurement range and test are calibrated,which provides technical supportfor large-caliber cameras'accurate test.The following research work has been done in this paper:Firstly,according to the spatial distribution function of light wave propagation,the influence of material surface roughness on light scattering is demonstrated.The modified Torrance-Sparrow model is used to fit the BRDF of rough material surface,and the stray light is modeled and analyzed with other models,respectively.The experimental results show that the simulation accuracy of the modified Torrance-Sparrow model is 2-3 magnitude higher than that of other models.magnitude.In order to facilitate the accurate modeling and simulation of stray light by software,the BRDF of different material surfaces is fitted into a standard database by combining the measured scattering data with the modified model,which provides a basis for stray light measurement and calibration analysis.Secondly,the different stray light test methods of the camera are discussed.The mathematical model is used to derive the camera stray light coefficient(V)is the sum of PST integrals of different fields of view.It is proved that the PST test can accurately estimate the distribution of stray light in different fields of the camera.A large-caliber,high-precision PST test method is proposed around the large-caliber stray light test technology,and three key techniques for improving test capability are analyzed.Then,the key technology——high brightness uniform target simulation technologyto improve the measurement capability of large-caliber and high precision PSTis studied.The target analog source collimator is designed,and the BRDF model of the key optomechanical surface is modeled by different scattering models.The stray light suppression ability of the collimator in the out-of-axis field of view is analyzed.The stray light produced by the mirror defect is analyzed according to the glass surface defect and the contaminant grade.In addition,Flattened Lorentzian function is used to shape the target simulation laser source,which realizes high-energy,collimation and uniform target simulation.The simulation analysis of the output energy and spot uniformity of the high brightness uniform target simulation system is carried out,which verifies the effectiveness of the laser shaping technology.Thirdly,the key technology of improving the measurement ability of large-caliber and high precision PST——high efficiency stray light suppression technology is studied.In order to improve the ability of the test system to suppress stray light in the environment,using the extinction principle of"absorption+reflection"and using a black two-column extinction chamber,the reflection,scattering and stray light in the outer wall of the camera under test are effectively suppressed.In addition,based on MIE scattering theory,the scattered stray light from air in a double cylinder tank is analyzed and calculated.The effect of scattered stray light from air on the measurement accuracy is suppressed by using efficient filtering method.Finally,the key technology to improve the measurement ability of large caliber and high precision PST——PST test accuracy calibration technologyis studied.According to the limit detection ability of the detection system and the irradiance of the simulated light source,the measurement range of the PST test system with large-caliber and high precision is calculated.The main factors affecting the improvement of the measurement ability are studied,and the corresponding measurement accuracy of the PST test limit of the system is analyzed.In addition,a special calibration system PST test capability is designed by combining the modified Torrance-Sparrow model with the measured surface scattering properties.