Fresnel diffraction of a Gaussian laser beam by polished metal cylinders

A laser beam touching the periphery of a polished cylinder is subjected to both diffraction and reflection. In the area where diffracted light and reflected light interact the resulting intensity distribution differs from the pattern predicted by diffraction theory for a sharp edge. The difference increases with cylinder radius. In this paper it is shown that a good description of the resulting intensity pattern is obtained by adding the reflected light amplitude to the diffracted amplitude as predicted by the Fresnel-Kirchhoff theory for a sharp edge.