Minute details detection through Fresnel diffraction domain

The capability of distinguishing fine details or perturbations in simple structures by means of Fresnel-domain diffraction is shown. Through numerical calculations it is shown that the greater the number of Fresnel zones considered in the diffraction setup the larger differentiability is reached. To illustrate our proposal the case of a circular clear aperture in an opaque screen with fine details of variable dimensions and subtending different number of Fresnel zones is studied. It is shown that by taking advantage of the Fresnel-domain diffraction it is possible to distinguish details or defects with area larger than or equal to 1% of the initial structure area, without any kind of mechanical contact between the diffracting structure and the recording media.