Binary graphic printer system having an electronic screen with shift control suited for rescreening

摘要

Ink jet and xerographic binary graphic printers are disclosed which make reproductions by marking the pixels within a raster pattern on a copy sheet with a high or low density (e.g. black or white) mark in response to electrical printing signals. The printing signals are generated by comparing the magnitude of video signals representative of a continuous tone raster image with electrical screen signals organized into halftone cells according to a pattern. A shift circuit processes received video signals and identifies the center of the black (or white) video signals within the confines of a screen halftone cell. The pattern of screen signals within a halftone cell is shifted to the center of the black video signals. The cell shifting suppresses beat frequencies in reproductions of originals containing screens or image detail with frequencies near that of the electrical screen.