Multiple-plane image formation by Walsh zone plates

A radial Walsh filter is a phase binary diffractive optical element characterized by a set of equal-area concentric rings that take the phase values 0 or π, corresponding to the values +1 or -1 of a given radial Walsh function. Different radial Walsh filters demonstrated characteristic self-similar focusing properties. Therefore, a Walsh filter can be re-interpreted as an aperiodic multifocal zone plate, capable to produce images of multiple planes simultaneously in a single output plane of an image forming system. In this paper, we report the achievement of multiple-plane images obtained with radial Walsh filters working as aperiodic diffractive lenses.