Research On The Characteristic Of Scattering Randomness And Depolarization In Polarimetry

The optical properties reflect the properties of the substance in optical phenomena.They provide objective judgment basis for the process of target detection,recognition and classification.Research on optical properties is developing rapidly.It is important and urgent to mine more effective target feature information for specific optical phenomena.In this thesis,the scattering characteristics,depolarization characteristics and the constraint relationship between them are studied respectively to solve the problems of low accuracy,single representation,insignificant difference and incomplete description of the relationship between different characteristics.Relevant work provides theoretical support and method reference for increasing the dimension of target feature information and perfecting the optical feature model of the target,which is beneficial to enlarge the difference of optical characteristics between different substances,and has practical significance in distinguishing natural objects from camouflage materials,water from oil substances.The research work of this thesis is summarized as follows:A Mueller matrix measurement platform based on bidirectional rotation compensation method is constructed to extract the polarization information of the target by polarization generator and analyzer.The influence of the target on polarized light is reflected by Mueller matrix.Based on the parameterized form of Mueller matrix in Fresnel reflection,the relations between Mueller matrix and incidence Angle and optical constant are constructed to check the accuracy of Mueller matrix measurement data with amplitude ratio and the variation of phase difference.The experimental results show that the platform can accurately obtain the polarization information of the experimental samples,and the experimental data are objective and reliable.A scattering mechanism characterization model based on symmetric scattering matrix is proposed to solve the problem of low accuracy in characterizing the main scattering mechanism.This model uses Cameron decomposition theory to extract the symmetric part of the scattering matrix.Combining the definition of rotation invariant,a characterization parameter of the scattering mechanism called symmetric rotation invariant angle is obtained from the Mueller matrix to improve the characterization accuracy of the scattering mechanism in the surface reflection process.According to the meaning of symmetric rotation invariant angle in different value ranges,scattering mechanism difference interval(SMDI)is presented to represent the difference of scattering mechanism between different objects,which is helpful to distinguish different substances in the case of multi-angle measurement.The experimental results show that SMDI can distinguish natural objects from camouflage materials by the difference of scattering mechanism with the change of incident angle,as well as water and oil substances.A Mueller matrix decomposition model based on scattering superposition is proposed to solve the problem that the depolarization index is general and single in describing the depolarization characteristics of the target.In this model,the Mueller matrix is decomposed into four submatrices representing different scattering types.The influence of scattering superposition on depolarization process is reflected through different combinations of each submatrix.Depending on the depolarization process,two characteristic parameters called diagonal scattering depolarization coefficient(DSDC)and cross scattering depolarization coefficient(CSDC)are defined to refine the characterization form of depolarization characteristics,which is helpful to distinguish different substances with similar depolarization index.The experimental results show that DSDC and CSDC can amplify the difference of depolarization characteristics between different objects,so as to distinguish leaves and camouflage coatings,soil and camouflage plates.They can also reflect the specific scattering superposition form and the continuous range in the multi-angle measurement data,thus distinguishing water and oil substances.A relational model called Entropy-Depolarization-Anisotropy(E-D-A)relation is proposed to solve the problem that the description of the relationship between scattering randomness and depolarization is not comprehensive in Entropy-Depolarization(E-D)relation model.Through introducing the scattering anisotropy,E-D-A relation reflects The relationship between scattering randomness and depolarization in higher dimensions.It not only maintains The two-dimensional relationship between scattering entropy and depolarization index,but also highlight The three-dimensional relationship between scattering anisotropy and depolarization index,which makes up the defect that the E-D relation model does not describe the target characteristic relation completely.The simulation and experimental results show that the E-DA relation model is consistent with the actual experimental data distribution and can provide the target characteristics of higher dimensions.With expanding the difference between different features in E-D relation,E-D-A relation is helpful to distinguish different objects.