| 摘要 |
<p>Disclosed are apparatus and methods for producing halftone screens (color separations) from continuous tone intensity signals that are supplied by an optical scanner (12). A digital signal processor (10) processes the continuous tone intensity values to establish memory maps (18-6, 18-7, 18-8 and 18-10) which, in conjunction with a digital data output device (34) (e.g., a laser printer or a conventional image setter), produce the desired halftone screens. In producing halftone screens having a screen angle that does not substantially differ from 90° (e.g., the 90°, 105°, and 75° screen angles of the yellow, cyan and magenta color separations in conventional four color halftone printing), the digital signal processor (10) utilizes a dither matrix (Figure 4) that is arranged to produce each halftone dot of the corresponding halftone screen at the desired screen ruling. In producing halftone screens having a screen angle that substantially differs from 90° (e.g., the 45° screen angle used in the black halftone color separation in conventional four color halftone printing), the digital signal processor (10) utilizes a dither array that properly positions the halftone dots of the resulting halftone screen and, in addition, establishes the desired screen ruling.</p> |
