HIGH RESOLUTION HALFTONE MICROIMAGES AND METHOD THEREFOR

摘要

High resolution microimages of continuous tone photographs must be prepared in halftone form to enable inexpensive duplication of the microimages by conventional graphic arts processes. The halftone pattern in such microimages must have a spatial frequency of not less than about 40 line pairs per millimeter in order to enable the projection of an acceptably detailed enlarged image. In the present invention, such halftone microimages are prepared using an ultra-high resolution gradiers density screen having therein an image of an interference fringe field resulting from an exposure of a perform of the screen to two interfering mutually coherent beams of radiation.