Raster exposure system for electrographic copier - uses separate raster cylinders during a second exposure

摘要

The original is exposed using a scanning line optical system in conjunction with a rotating photoreceptor drum. During the second exposure of the reversal process (NP process) a selected grid, raster or point pattern is projected on to the image. The grid, raster or point pattern is carried on one of several cylinders. The patterns used for the several colour separation images in colour printing are aligned at various angles to eliminate moire patterns. In monochrome copying the use of a raster improves half-tone gradation.