Abstract

High-efficiency diffractive elements rely on Bragg or volume diffraction. The flexibility of computer generation and plotting of hologram intensity patterns has focused on two-dimensional elements. We consider the use of several such two-dimensional elements to make a volume element. The design of the three-dimensional structure is based on solving the inverse, or synthesis, problem with the Rytov approximation. We have concentrated on the fabrication of a high-efficiency element that can transform a Gaussian laser beam into a uniform distribution of light. Ideally, we require a pixel size of a few microns, but we can expect only around 10 to 20 µm (i.e., around 100 lines/mm resolution) if we use a Linotype 500 laser printer. A sandwich of two-dimensional computer-originated holographic elements can, in principle, improve on this by reducing the effective size of each diffracting element. After we have determined structure of the diffracting element, an optimal binary coding scheme (direct binary search) is used to represent it.

© 1990 Optical Society of America