基于穆勒矩阵的水面溢油偏振散射特性研究

【作者】 周静；

【导师】 任侃；

【作者基本信息】 南京理工大学 ， 光学工程（专业学位）， 2021， 硕士

【摘要】 水面溢油污染会对生态环境和人类健康造成巨大危害,因此,能够及时发现水面溢油并采取措施对生态环境的保护具有重要意义。传统光学遥感溢油检测研究中,随着油膜厚度变薄,其光学特性发生了显著变化,油膜与背景水体之间的差异减小,水面油膜检测的难度也随之增大。随着遥感溢油检测技术的不断发展,偏振信息在溢油污染检测中的重要性逐渐显露出来,水面溢油具有显著的偏振散射特性,将描述偏振散射特性变化的穆勒矩阵应用于遥感探测,能够很好地提高水面溢油检测能力。针对水面溢油目标的偏振散射特性,本文在偏振光学的理论基础上,分析了目标穆勒矩阵的测量方法,搭建了多角度穆勒矩阵测量系统,设计了目标表面光学特征的提取方法,建立了能够估计散射相似性参数的函数关系,通过对目标偏振散射特性的分析提出了散射相似性参数差异(Scattering Similarity Parameter Difference,SSPD)这一特征参数,结合振幅比、相位延迟和SSPD这三个光学特征,在区分水和油膜方面具有重要意义。主要研究内容归纳如下:(1)阐述了偏振光学的理论基础,包括偏振光、光学系统及目标散射过程的数学表征方法。重点介绍了穆勒矩阵的偏振特性,以及散射矩阵、协方差矩阵和相干矩阵的定义。(2)对目标表面光学特征的提取展开研究。根据穆勒矩阵测量系统介绍了测量方法,将穆勒矩阵转换成穆勒琼斯矩阵,从中提取振幅比和相位延迟。对散射矩阵进行Pauli分解,研究目标与典型散射体之间的散射相似性参数,基于菲涅尔反射条件,建立散射相似性参数与振幅比、相位延迟的函数关系,从而对散射相似性参数进行估计。(3)利用穆勒矩阵测量装置测量水和油膜样品的穆勒矩阵,分别计算样品的振幅比、相位延迟和散射相似性参数,分析样品间偏振散射特性差异,通过比较散射相似性参数估计值和测量值,证明推导得到的函数关系的可靠性,进一步提出能扩大水和油膜之间散射特性差异的特征参数SSPD。实验结果表明,水和油膜的振幅比、相位延迟有明显差异,可以作为区分水和油膜的重要依据。GII油、仪扬油、凝析油与水之间的SSPD差值的均值分别为0.1223、0.1291和0.1305,放大了水和油膜之间散射特性差异,且在SSPD等于0时,水和三种油膜的入射角相差约4°,可以较为容易地区分水和油膜。本文对目标的偏振散射特性展开研究,提取振幅比和相位延迟,进一步提出特征参数SSPD,综合这三个光学特征共同区分水和油膜为水面溢油检测提供了方法参考。更多还原

【Abstract】 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.更多还原