Multiple-plane image formation by Walsh zone plates
A radial Walsh filter is a phase binary diffractive optical element characterized by a set of concentric rings that take the phase values 0 or pi, corresponding to the values 1 or -1 of a given radial Walsh function. Therefore, a Walsh filter can be reinterpreted 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 experimentally demonstrate for the first time the focusing capabilities of these structures. Additionally, we report the first achievement of images of multiple-plane objects in a single image plane with these aperiodic diffractive lenses.