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1. (WO2005108083) METHOD FOR DETERMINING COLOUR VALUES AND/OR DENSITY VALUES, AND PRINTING DEVICE FOR IMPLEMENTING SAID METHOD

Pub. No.:    WO/2005/108083    International Application No.:    PCT/EP2005/004608
Publication Date: Nov 17, 2005 International Filing Date: Apr 29, 2005
IPC: B41F 33/00
Applicants: HEIDELBERGER DRUCKMASCHINEN AG
GRETAG-MACBETH AG
EHBETS, Peter
GEISSLER, Wolfgang
KOHLBRENNER, Adrian
Inventors: EHBETS, Peter
GEISSLER, Wolfgang
KOHLBRENNER, Adrian
Title: METHOD FOR DETERMINING COLOUR VALUES AND/OR DENSITY VALUES, AND PRINTING DEVICE FOR IMPLEMENTING SAID METHOD
Abstract:
During the inline measurement of sheets to be printed during the printing process, measured value deviations are created in relation to external reference measurements on sheets in stable conditions. Said measured value errors are caused by the effects of the colour separation and by the drying effects of the sheet. In order to obtain colour measured values that are compatible with external reference measurements, said measured value errors are eliminated or corrected by a combination of measuring and calculating correction steps. The measured value correction is carried out on the basis of a model that describes the measured value error as a combination of three error contributions caused by the surface effect, the layer thickness modulation and the light trap. Three degrees of freedom quantified by three correction functions are introduced for the correction. Said correction functions are stored in a correction database as correction parameters, and a specific set of correction parameters is provided for each combination of environment parameters of the printing process in question. The inventive correction method enables the conversion of measured values between three states corresponding to direct measurement during the printing process, measurement on a printed sheet that is still wet, and measurement on a dried printed sheet.