Surface analysis using polarisation

• Main Author: Gul-E-Saman
• Published: University of York 2012
• Subjects: 006.42
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.583351

Unpolarised light incident on a surface acquires partial polarisation due to the orientation of the dipoles in the scatterer. This thesis focuses on the use of polarised light for diffuse reflectance for surface analysis. Since, the state of polarisation is acquired on interaction with the surface, the polarised light contains information about the surface properties (of the scatterer). A great amount of research has been carried out in computer vision for surface analysis using image analysis techniques. Recently, the trend has been to combine optical techniques with computer vision in order to arrive at better analysis techniques by methods that analyse the intrinsic qualities of the surfaces under study. An overview of the recent work that has been carried out in the field is given in Chapter 2 in context to this thesis. The contributions of this thesis are: 1. the robust computation of polarisation image using M-estimators, the smoothing of phase of polarisation by using directional statistics and using the calculated parameters for effective surface recovery, 2. estimation of the refractive index of a diverse set of surfaces of known and unknown refractive indices and using the estimates for segmentation, 3. estimating the complex refractive index which incorporates the phenomenon of absorption by two methods existing in literature, using a. ellipsometry and b. multiple polarisation measurements while building up on the case of surface analysis being related to its optical properties and 4. carrying out a preliminary study by modifying the geometric factor of the polarimetric bidirectional reflectance distribution function. Experimental evidence has been presented in the thesis for the methods that have been used for a variety of objects with varying geometrical and surface properties. The approach in this thesis has been to adopt simple and adaptable techniques that can be easily employed without the use of sophisticated equipment.