Research On Polarization Scattering Characteristics Of Oil Spill On Water Surface Based On Mueller Matrix

Oil spill pollution on the water surface has caused great harm to the ecological environment and human health.Therefore,it is of great significance to detect the oil spill on the water surface in time and take measures to protect the ecological environment.In traditional optical remote sensing oil spill monitoring research,as the thickness of the oil film becomes thinner,its optical characteristics have changed significantly,the difference between the oil film and the background water body decreases,and the difficulty of detecting the oil film on the water surface also increases.With the continuous development of remote sensing oil spill detection technology,the importance of polarization information in oil spill pollution detection has gradually emerged.Oil spills on the water surface have significant polarization scattering characteristics.The application of the Mueller matrix which describes the variation of polarization scattering characteristics to remote sensing detection can improve the detection ability of oil spill on the water surface.Aiming at the polarization scattering characteristics of oil spill target on water surface,in this paper,based on the polarization optics theory,the measurement method of target Mueller matrix is analyzed,a multi angle Mueller matrix measurement system is set up,the method of extracting optical features of target surface is designed,a functional relationship which can estimate scattering similarity parameters is established,and the characteristic parameter of scattering similarity parameter difference(SSPD)is proposed through the analysis pf the polarization scattering characteristics of the target.The combination of amplitude ratio,phase retardation and SSPD is of great significance in distinguishing water from oil film.The main research contents are summarized as follows:(1)The theoretical basis of polarization optics,including the mathematical characterization of polarized light,optical system and target scattering process,are described.The emphasis is on the polarization characteristics of the Mueller matrix,and the definitions of the scattering matrix,covariance matrix and coherency matrix.(2)The extraction of optical features of target surface is studied.According to the measurement system of Mueller matrix,the measurement method is introduced.The Mueller matrix is transformed into Mueller Jones matrix,and the amplitude ratio and phase retardation are extracted from it.The Pauli decomposition of the scattering matrix is carried out to study the scattering similarity parameters between the target and the typical scatterers.Based on the Fresnel reflection condition,the functional relationship among the scattering similarity parameters,the amplitude ratio and phase retardation is established,so as to estimate the scattering similarity parameters.(3)The Mueller matrices of water and oil film samples are measured by Mueller matrix measurement device,and the amplitude ratio,phase delay and scattering similarity parameters of samples are calculated respectively.The polarization scattering characteristic differences between samples are analyzed.The reliability of the derived functional relationship is proved by comparing the estimated and measured values of scattering similarity parameters.Furthermore,the characteristic parameter SSPD which can magnify the scattering characteristic difference between water and oil film is proposed.The experimental results show that the amplitude ratio and phase retardation of water and oil film are obviously different,which can be used as an important basis for distinguishing water from oil film.The mean values of SSPD differences between GII oil,Yiyang oil,Ningxi oil and water are 0.1223,0.1291 and 0.1305 respectively,which magnify the difference of scattering characteristics between water and oil film.When SSPD is equal to 0,the difference of incident angles between water and three kinds of oil film are about 4°,which makes it easier to distinguish water from oil film.In this paper,the polarization scattering characteristics of the target are studied,the amplitude ratio and phase retardation are extracted,and the characteristic parameter SSPD is further proposed.The three optical characteristics are combined to distinguish water from oil film together to provide a method reference for detecting oil spill on the water surface.