Patent ID: 8351085

Claim:
A moiré-free halftone image forming method for reproducing an image using a different halftone screen with hexagonally tiled clusters for each colorant associated with an image rendering device, the method comprising: a) defining a first colorant halftone screen with hexagonally tiled clusters having a first fundamental frequency vector V c1 , a second fundamental frequency vector V c2 , and a third fundamental frequency vector V c3 , where V c3 =V c1 −V c2 ; b) defining a second colorant halftone screen with hexagonally tiled clusters having a first fundamental frequency vector V m1 , a second fundamental frequency vector V m2 and a third fundamental frequency vector V m3 , where V m3 =V m1 −V m2 ; c) defining a third colorant halftone screen with hexagonally tiled clusters having a first fundamental frequency vector V y1 , a second fundamental frequency V y2 and a third fundamental frequency V y3 , where V y1 =V m1 +V c2 , V y2 =V m2 −V c3 and V y3 =V y1 −V y2 ; d) generating the first colorant halftone screen, the second colorant halftone screen and the third colorant halftone screen; e) applying the first colorant halftone screen to the image to produce a first colorant halftone output, applying the second colorant halftone screen to the image to produce a second colorant halftone output, and applying the third colorant halftone screen to the image to produce a third colorant halftone output; and f) overlaying the first colorant halftone output, the second colorant halftone output and the third colorant halftone output to reproduce the image with a moiré-free halftone image.