Method and apparatus for scanning a document original, either black and white or color, and reproducing a corresponding halftone reproduction thereof either locally or at a remote location. A halftone signal is generated by pulse width modulating or comparing the scanned, or video, signal with a periodic...http://www.google.fr/patents/US4149183?utm_source=gb-gplus-shareBrevet US4149183 - Electronic halftone generator
