The zone plate and its role in holography

The classical Fresnel zone plate, with its alternate opaque and transparent zones, behaves like a lens which is simultaneously both converging and diverging. Improvements in the performance of such zone plates has recently led to some attention being given to their potential use as lenses in certain applications. The image formation involved in holography is strikingly similar to that characteristic of the zone plats and a hologram may be considered as a generalized zone plate. In this respect the sine-wave zone plate, in which the amplitude transmission is continuously distributed according to a sine-wave, is of primary importance. By examining the properties of such a plate it is possible to understand holographic image reconstruction.