Research On Data Processing And Quantification Of Polarization Imaging System

Polarization detection technology has become a hotspot for remote sensing detection,and it has shown wide application prospects in the inversion of atmospheric particles,cloud and aerosol microphysical properties and other applications.Performing high-precision polarization calibration is the guarantee of quantitative numerical inversion.In order to verify the detection capabilities of polarization detection instruments,it is of great scientific significance and engineering value to carry out laboratory polarization calibration and on-orbit polarization calibration research.Starting with the analysis of the characteristics of the polarization calibration source,considering the structural characteristics of the polarization remote sensing instrument,and combining the laboratory polarization calibration with the on-orbit polarization calibration,a polarization calibration method for the whole process of the life cycle of the multi-angle polarization imager was proposed.It provides data quality assurance for the performance evaluation and quantitative inversion of polarization remote sensing instruments,and has important theoretical and practical significance for high-precision aerosol and cloud inversion,atmospheric correction and other applications.In this treatise,combining with polarization optics principle and matrix optics theory,the full image plane polarization calibration model was established based on the optomechanical structure and imaging principle of the multi-angle polarization imager.Using this model,the article analyzed the instrument's own polarization effect mechanism,determined the polarization effect parameters that affect the instrument's polarization detection results and focuses on the causes of the parameter changes,and finally obtained the system-level polarization response matrix.In view of the fact that the multi-angle polarization imager is already in orbit without an on-board calibrator,the paper established a full-image polarization calibration model based on the water cloud zero degree of liner polarization(DOLP)calibration source.After explaining the relationship between the polarization characteristics of different cloud phase states and the scattering angle,the method of screening the zero DOLP radiation response values of water cloud pixels in different positions of the image plane was determined.Considering the characteristics of the instrument's large field of view,multi-spectral and time-sharing detection,this paper proposed a solution method for the full image polarization response parameters based on water clouds.The zero DOLP radiation response value was used to solve the filter-polarizer relative transmittance parameter,and the changes of the polarization channels of three different spectral bands within three years were compared.The 565 nm channel was selected as the spectral channel for later analysis.Using the field of view angle,zero polarization radiation response value and the filter-polarizer relative transmittance obtained in the previous step,the polarization degree of optical lens and the relative low-frequency transmittance parameters were solved.The variation of the 565 nm channel polarization degree of optical lens and the relative low-frequency transmittance with the angle of field were analyzed,and the change trend was fitted by the least square method to obtain the full-image distribution.Based on the above polarization effect parameters,the polarization response matrices in different fields of view were obtained by synthesizing the polarization effect parameters.By observing sun glint,high DOLP target,and using laboratory polarization calibration polarization response matrix as verification,the verification results show that the relative error between the central field polarization response matrix and the laboratory one is 1.22%,and the edge field DOLP reaches 0.077,which requires correction of the edge field data.Finally,the uncertainty analysis shows that the uncertainty of the polarization effect in the center field of view of the instrument is 1.27%,and the uncertainty of the edge field of view is 2.19%,which verifies the rationality of the full image on-orbit polarization calibration method.In order to verify the accuracy of the method of the full image polarization response parameters,this paper used the ocean sun glint DOLP simulation as a basis to implement the on-orbit polarization calibration method based on ocean sun glint,and extended to the quality control of the full image polarization calibration results.Firstly,the rough surface model of the ocean was established,and polarized radiation characteristics of the ocean sun glint are analyzed,and the calibration results of the four rough sea surface models were compared.By using the 6SV atmospheric radiation transmission model,this study calculated the top of the atmosphere(TOA)ocean sun glint polarization characteristics.The method introduced the quadratic term of the TOA polarization degree formula,and verified the significance of the quadratic term by t test,and further corrected the aerosol polarization effect.Finally,the solar zenith angle and correction coefficient look-up table were adopted,and the forward polarization observation results were obtained through simulation.This paper used POLDER3 polarization observation data to carry out the verification work.The relative error of the algorithm is better than 2%.The uncertainty analysis of the method shows that the combined uncertainty of the polarization degree of the method is 1.43%,which is consistent with the verification results.The algorithm is used to calibrate the polarization of MAPI.And the accuracy of the polarization calibration is about 2%,which meets the requirements of the instrument's polarization accuracy.In this treatise,according to the characteristics of the wide field of view,multi-spectral and polarization imaging of the MAPI,combined with polarization optics theory,a laboratory adjustable DOLP polarization calibration system was established.The polarizer with adjustable DOLP was designed and developed,and the possible ghosting problem was studied and evaluated.While expanding the measurement range of DOLP,the degrees of freedom of the polarizer with adjustable DOLP was reduced.The Stokes polarimeter was used to verify the production range of DOLP.The experimental results show that the polarizer can produce partially polarized light with a polarization degree ranging from 0 to 0.578,which lays the foundation for the future development of calibration sources.The polarizer with adjustable DOLP was used to perform polarization calibration on early model of MAPI.The relative error in the 565 nm channel is only 1.86%,which meets the technical specifications of the instrument.Finally,the uncertainty of the instrument is analyzed and calculated in detail,and the uncertainty is 0.9% in the DOLP range of 0.11-0.72.This result further verifies the rationality of the design of the adjustable DOLP polarization calibration source and provides a basis for the subsequent calibration of the instrument.