DESIGN OF PROJECTIVE ZONE PLATES AND THEIR FOCUSING PROPERTIES

Transmittances are designed by generation of a family of curves whose local geometry is similar to that of zone plates. The family is obtain ed by means of projective mapping in the normal direction of an initia l curve, so that all the curves of the family have a common evolute. T his property allows the prediction of the geometry of the focusing reg ion of the transmittance. Experimental results with an ellipse as the initial curve are shown. We show that the proposed zone plates can be considered a generalization of conventional zone plates. (C) 1997 Opti cal Society of America.