Refractive index estimation of naturally occurring surfaces using photometric stereo

Abstract

This paper describes a novel approach to the computation of refractive index from polarisation information. Specifically, we use the refractive index measurements to gauge the quality of fruits and vegetables. We commence by using the method of moments to estimate the components of the polarisation image computed from intensity images acquired by employing multiple polariser angles. The method uses photometric stereo to estimate surface normals and then uses the estimates of surface normal, zenith angle and polarisation measurements to estimate the refractive index. The method is applied to surface inspection problems. Experiments on fruits and vegetables at different stages of decay illustrate the utility of the method in assessing surface quality. © 2011 Springer-Verlag.