Shape from Diffuse Polarisation

When unpolarised light is reflected from a smooth dielectric surface, it is spontaneously partially polarised. This process applies to both specular and diffuse reflection, although the effect is greatest for specular reflection. This paper is concerned with exploiting this phenomenon by processing images of smooth dielectric objects to recover surface normals and hence height. The paper presents the underlying physics of polarisation by reflection, starting with the Fresnel equations. It is explained how these equations can be used to obtain the shape of objects and some experimental results are presented to illustrate the usefulness of the theory.