High efficiency diffractive lenses: Deduction of kinoform profile

The zone plates (diffractive lenses) are not commonly used as image formation systems owing to their low efficiency and multifocal characteristics. In this paper we make a revision of the Fresnel zone plate principles, and present various kinds of zone plates designed to solve the problem of obtaining a limited number of foci with higher efficiency. The purpose of this work was to design, by using Fermat’s principle, a zone-plate profile with high focusing efficiency in only one or two foci, while maintaining a low efficiency in the others. Applying Fermat’s principle to this task results in the kinoform profile of the plate. Calculation of the kinoform profile efficiency reveals that it is the best possible solution to this problem.