  In the last two decades, Fresnel diffraction (FD) of a plane wave from phase
steps has been systematically studied and applied for precise measurements of
light wavelength, and height and refractive index of the step. In this study we
formulate FD of cylindrical and spherical wavefronts from a transparent step in
transmission mode. It is shown that, the intensity distribution is a periodic
function along the lines parallel to the plate edge. The phase distribution in
this direction is a linearly varying function of the position squared, with a
slope depends on the light wavelength, the plate thickness and refractive
index, and the radius of wavefront curvature (RWC) on the observation plane.
Therefore, it has significant potential in optical metrology, by a single-shot
recording. The diffraction patterns are simulated and experimentally verified.
Also, the RWC and displacement are determined as examples of applications in
the experimental part of the report.
