Apparatus and method for improving black and color separation in halftoned images by printing black dots in a different screen phase

摘要

A K separation screen comprises a grid of dots located at fixed positions, with the screen angle for each color, including black, maintained at 45°. All of the primary color dots are printed at a predetermined screen frequency at predetermined locations. The black dots are also printed at a fixed screen frequency at predetermined locations. However, the black dots are printed in a different screen phase from the other colors, in particular, the phase offset is equal to one-half the screen frequency. Apparatus and a method are disclosed for generating the K separation screen using a cluster dot dithering array and offsetting the array pattern used to generate the colored halftone dots from the array pattern used to generate the black halftone dots.