B - Operations – Transporting – 41 – C
Patent
B - Operations, Transporting
41
C
101/71
B41C 1/04 (2006.01) H04N 1/40 (2006.01)
Patent
CA 1099148
ABSTRACT A method for the improved reproduction of edges associated with sharp changes in tone density during the engraving of screened printing forms with an engraving tool. The engraving tool is controlled by an engraving signal obtained from superposition of an image signal and a screening signal. The image signal is derived from scanning an original with a resolution which is twice as large in the scanning direction as that of the printing screen. Based on the higher resolution the image signal is digitalized into principal image values and additional intermediate image values. If a sharp change in the density defined as an edge occurs in the original a principal image value and the associated intermediate image values are combined into one memory word after the image values have been recoded into values of shorter word lengths and intermediately stored. If no edge is present in the original only the principal image values are intermediately stored as memory words. The combined memory words are separated into the principal image values and the intermediate image values when read out of the memory. The principal image values are superimposed onto the screening signal at the instants of periodically recurrent amplitude values of the screening signal, when the engraving tool cuts the cups and the associated intermediate image values are superimposed before said instants. Thus, the engraving information for each cup consists of two image values, whereby the cups for a sharp change in tone density are shifted relatively to the printing screen toward a higher density level so as to accomplish improved reproduction of the edges. Storing the image values as described allows the capacity of the memory to remain constant although a bigger number of image values are processed.
311117
Hell (dr. -Ing. Rudolf) Gmbh
Smart & Biggar
LandOfFree
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