A method to correct for surface scattering in spatial frequency domain imaging (SFDI) is presented. The use of a modified analytical solution of the radiative transfer equation allows calculation of the reflectance and the phase of a rough semi-infinite geometry so that both spatial frequency domain reflectance and phase can be applied for precise retrieval of the bulk optical properties and the surface scattering. For validation of the method, phantoms with different surface roughness were produced. Contrarily, with the modified theory, it was possible to dramatically reduce systematic errors due to surface scattering. The evaluation of these measurements with the state-of-the-art theory and measuring modality, i.e., using crossed linear polarizers, reveals large errors in the determined optical properties, depending on the surface roughness, of up to ≈100 % . These results were confirmed with SFDI measurements on a phantom that has a structured rough surface.
Keywords: absorption coefficient; bidirectional reflectance distribution function; radiative transfer equation; reduced scattering coefficient; spatial frequency domain imaging; surface scattering.
(2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).