B - Operations – Transporting – 41 – F
Patent
B - Operations, Transporting
41
F
101/101, 354/21
B41F 31/02 (2006.01) B41F 33/00 (2006.01) G01J 3/50 (2006.01)
Patent
CA 1216943
PROCESS AND APPARATUS FOR EVALUATING PRINTING QUALITY AND FOR REGULATING THE INK FEED CONTROLS IN AN OFFSET PRINTING MACHINE ABSTRACT OF THE DISCLOSURE The printed sheets are scanned, by image elements, immediately behind the last printing mechanism, with one or several measuring heads. Suit- able dimensions of an image element range from approximately 1 x 1 mm2 to 10 x 10 mm2. In each image element the reflectance is measured in four spectral ranges (infrared for black, red for cyan, green for magenta and blue for yellow). The measured reflectance values are converted by means of Neugebauer equations into surface coverages in a demasking step and inputted to a computer for evaluation. With the same measuring device, both the reference values associated with OK sheets, and the actual values associated with continu- ous printing, are measured. The computer compares the measured data, weights them with respect to such factors as surface coverage, foreign color component and the environment of a respective image element, and produces a regulating signal to control the ink feed elements. The color coordinates (X,Y,Z) may be deter- mined from the surface coverage values of the four colors in a parallel computer program. Image elements which are important for the visual appearance of an image are given a high weight. A quality measure may be determined from the weighted comparison of reference and actual values to change the visual appearance. With this process it is possible to control the ink feed elements of a multicolor printing press by direct on-line measurement of the printed image, without using color measuring strips.
466916
Boegli Rolf
Keller Guido
Ott Hans
Spiess Andreas
Fetherstonhaugh & Co.
Gretag-Macbeth Ag
Heidelberger Druckmaschinen Ag
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