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Deducing ink thickness variations by a spectral prediction model
Author(s) -
Hersch Roger D.,
Brichon Mathieu,
Bug Thomas,
Amrhyn Peter,
Crété Frederique,
Mourad Safer,
Janser Hebert,
Jiang Yufan,
Riepenhoff Matthias
Publication year - 2009
Publication title -
color research and application
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.393
H-Index - 62
eISSN - 1520-6378
pISSN - 0361-2317
DOI - 10.1002/col.20541
Subject(s) - inkwell , halftone , reflection (computer programming) , materials science , reflectivity , transmittance , volume (thermodynamics) , optics , computer science , composite material , optoelectronics , physics , pixel , quantum mechanics , programming language
Most existing techniques for regulating the ink flow in offset presses rely on density measurements carried out on specially printed patches. In the present contribution, we develop a methodology to deduce ink thickness variations from spectral measurements of multichromatic halftone patches located within the printed page. For this purpose, we extend the Clapper‐Yule spectral reflectance prediction model by expressing the transmittance of the colorants composed of superposed inks as a function of the ink transmittances and of fitted ink layer thicknesses. We associate to each ink an ink thickness variation factor. At print time, this ink thickness variation factor can be fitted to minimize a difference metric between predicted reflection spectrum and measured reflection spectrum. The ink thickness variations deduced from multichromatic halftones allow to clearly distinguish between normal ink volume, reduced ink volume, or increased ink volume. This information can then be used for performing control operations on the printing press. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 432–442, 2009