Calibration Research For Amplitude Divided Polarimetric Imaging System

Polarization is an important feature of light as an electromagnetic transverse wave,which carries a wealth of information.Compared to the traditional remote sensing imaging detection,polarimetric imaging detection has the characteristics of highlighting target,identifying true and false,classifying and identifying,retrieving the physicochemical and texture properties of the target surface.Especially in the cloud and aerosol detection,the key parameters can be obtained such as aerosol type,optical thickness,particle distribution and so on,which has important application value.Currently,according to the difference of polarization detection scheme,polarimetric imaging system can be divided into time-divided,amplitude-divided,aperture-divided,focal-plane-divided polarimetric imaging,modulation polarization imaging and other types.The amplitude divided polarimetric imaging system is a commonly used simultaneous polarization imaging scheme,which works in the way of single lens imaging,beam splitter and multichannel detection.There is a certain polarization effect in the imaging optical system,which will change the polarization state of the beam and have a certain influence on the precision of polarization detection.At the same time,because the polarization information is obtained through the difference of the intensity received by each channel.The difference of system transmittance between different channels,the polarization parameters of detector and the inconsistency of detector response will have an impact on the intensity of each channel.Therefore,the amplitude divided polarimetric imaging system must be calibrated to correct the system errors above,so that the accuracy of polarization detection can be ensured,and the foundation for the accurate application of polarization detection data will be laid.In this paper,the following research work is carried out in view of the demand of polarization and radiation calibration in the amplitude divided polarimetric imaging system.To describe the influence of optical system on polarization transmission,a three-dimensional global coherence matrix is proposed.And a three-dimensional polarization radiation transmission model of partially polarized light in optical system is established,which provides a theoretical basis for system calibration.The influence of the polarization effect on the polarization transmission is calculated by using this three-dimensional polarization ray tracing algorithm for the optical system of the partial amplitude polarization imaging.In order to describe the polarization characteristics of optical system,the basic polarization parameters of optical system,diattenuation and retardance,are obtained by the method of characteristic decomposition of three-dimensional polarization matrix.And the diattenuation and retardance distribution of the amplitude divided polarimetric imaging system are analyzed by using a three-dimensional polarization ray tracing algorithm.The polarization matrix of the nonideal linear polarizer is described,and the influence of the extinction ratio parameters is analyzed.In order to get the polarization parameters of polarization imaging system,the corresponding calibration scheme is put forward,and the calibration physical model is established.Finally,the relevant experimental calibration is carried out for the system.To realize the radiometric calibration of the amplitude divided polarimetric imaging system,a radiometric calibration model of each channel is established based on the three-dimensional polarization radiative transfer model,and the simulation experiment is carried out.The result shows that the calibration scheme can get the radiation parameters of each channel of the system,and correct the difference of the radiative response among the channels,so as to achieve the radiometric calibration of the polarization detection system.In order to achieve the polarization calibration of the amplitude divided polarimetric imaging system,the polarization calibration model of the system is established based on the basic principle of the split amplitude polarization detection,and verified by experiments.The result shows that the calibration scheme can correct the measurement error caused by the polarization error parameter,and achieve the polarization calibration of the polarization detection system,and finally improve the accuracy of polarization measurement.The on orbit calibration scheme is analyzed,and the on orbit calibration model of sea glint is established,and the spaceborne analyzer calibration method is put forward,and finally provides the basis for the follow-up system on orbit calibration scheme.