Separate determination of scattering and absorption by using the spatially resolved intensity distribution

With spatially resolved reflectance, a scattering sample is illuminated in a point-like manner and the light distribution created by the light propagation in the medium is measured. This can be done, for example, by contact-free illumination and detection with a CCD camera (picture on the right) or by measuring at different distances in contact with the sample using optical fibers. If the light is additionally illuminated at an angle to the surface normal, it is possible to obtain additional information from the lateral displacement

obtained from the lateral displacement. By nonlinear regression with the theory of radiative transfer, the optical properties, the effective scattering coefficient µs’ and the absorption coefficient µa, and a parameter, more effectively scattering coefficient µ_s', absorption coefficient µ_a and a parameter for surface roughness, can be determined. For the solution of the radiation transport equation, analytical or numerical solutions (Monte Carlo method) can be used depending on the sample geometry.