PATTERN GENERATION WITH AN EXTENDED FOCAL DEPTH

The depth of focus of light patterns can be extended, within given tol erances, beyond the classical limits. For a quantitative evaluation we introduce a degree of depth-of-focus extension and a three-dimensiona l energy-distribution efficiency. The basic limitations involved in de pth-of-focus extension are discussed. A coherent system in which the i nput is optimized for a desired output pattern is presented. An exampl e of a pattern containing diffraction-limited line segments and a 4 ti mes improvement in depth of focus is demonstrated. This task is much m ore difficult than generating patterns of isolated light spots in whic h the depth of focus is extended beyond an order of magnitude. (C) 199 8 Optical Society of America.