ENCODING TECHNIQUE FOR DESIGN OF ZERO-ORDER (ON-AXIS) FRAUNHOFER COMPUTER-GENERATED HOLOGRAMS

Diffractive optical elements able to generate zero-order (on-axis) dis tributions with phase as well as amplitude distributions are described . The proposed elements are surface relief plates, i.e., phase-only el ements, that are based on the concept of computer-generated masks foll owed by common etching processes. The encoding method assumes fixed sp atial partitioning of the cell and a phase-only value allocated to eac h subelement. The reconstructed amplitude and phase distributions cont ain imperfections (noise) resulting from the encoding process. Methods of error reduction and improvements are provided. (C) 1997 Optical So ciety of America.