Method for preparing color separation printing patterns

Abstract

In a method of preparing color separation printing patterns from a multi-color original design, the design is irradiated by light and multi-color light components reflected from minute picture elements constituting the design are detected. The detected light components are converted to picture element data representative of the optical energy level of the reflected light corresponding to each picture element. The picture element data are stored and filtered to form quantized picture element data indicative of several series of reflected light components respectively falling within different preselected ranges of color. This is done by comparing successive picture element data to detect significant differences in energy level indicative of color changes. The reason for each substantial difference in output level is determined, e.g., pattern defect or imperfection, and the filtered picture element data are stored along with change codes indicative of the reason for the difference. The color of the filtered picture element data is identified by comparison with predetermined stored sample color data. The picture element data are then modified in accordance with the change codes to comply with particular printing conditions or to correct the determined imperfections or defects arising in the original design before the data are supplied to a photomodulator which modulates a laser beam impinging on a photosensitive film for black-and-white reproduction of a predetermined identified color of the original design.