Digital Screening and Halftone Techniques for Raster Processing

摘要

The development of raster processing programs at USAETL has included programs for the generation of raster plot data containing cartographically symbolized features as well as the more widely investigated raster-to-vector software. Raster plot data may be used to generate film negatives with open window areas over which mechanical screens can be placed by conventional contact printing techniques. These areas can also be filled with digitally generated screens, a capability unique with the raster approach. Further, since most available raster plotting hardware does not permit the modulation of each pixel for intensity, it is desirable to control groups of pixels in order to approximate a halftone dot for color or density control. A study was made to determine the suitability of the 25 micron pixel raster on the Digital Laser Platemaker for the generation of digital screens for absolute color and process color printing. Tests will be conducted to establish screen pattern and angle criteria to achieve desired results without moire. An associated literature search resulted in a fairly comprehensive bibliography of work published in the digital screening field. (Author)