|
| US4084183 | 11 avr. 1975 | 11 avr. 1978 | Dr. Ing. Rudolf Hell GmbH. | Method for the electro-optical reproduction of half-tone pictures |
| US4149183 | 21 mai 1976 | 10 avr. 1979 | Xerox Corporation | Electronic halftone generator |
| US4149195 | 22 déc. 1977 | 10 avr. 1979 | Dr. Ing. Rudolf Hell GmbH | Method and apparatus for producing rastered printed forms |
| US4196451 | 28 juil. 1978 | 1 avr. 1980 | Xerox Corporation | Electronic halftone generator |
| US4897734 | 24 oct. 1986 | 30 janv. 1990 | Canon Kabushiki Kaisha | Image processing apparatus |