The use of half-tone screens in Fresnel zone plate imaging of incoherent sources

Abstract

An off-axis Fresnel zone plate may be used as a large-area “coded” aperture for imaging incoherent sources. The zone plate is sufficiently coarse that only shadow-casting, and not diffraction, is involved. It is shown here that the usefulness of this system can be greatly increased by using a half-tone screen to introduce a spatial carrier frequency and heterodyne the object spectrum into the passband of the zone plate.