Patent ID: 7675651

Claim:
An image forming method for digitally reproducing a moiré-free color halftone image using a halftone screen set consisting of a halftone screen for each color, the method comprising: using a color halftoning screening apparatus to perform: defining a first color halftone screen having a first fundamental frequency vector V c1 and second fundamental frequency vector V c2 ; defining a second color halftone screen having a first fundamental frequency vector V m1 and second fundamental frequency vector V m2 ; defining a third color halftone screen having a first fundamental frequency vector V y1 and second fundamental frequency vector V y2 ; and, selecting the values of the fundamental frequency vectors V c1 , V c2 , V m1 , and V m2 such that the combinations satisfy the following: V c1 −V m1 =−½ V m2 , V m2 −V c2 =−½ V c1 , and V y1 equals one of V c1 , V c2 , V m1 , and V m2 ; and using said halftone screens, as further specified by said selected values of said fundamental frequency vectors, in an image forming apparatus for digital reproduction of a moiré-free color halftone image.