METHOD AND APPARATUS FOR IDENTIFYING METALLIC PLATE PRINT SHEET

摘要

PROBLEM TO BE SOLVED: To provide a method and apparatus for accurately detecting a color mark attached to a metallic plate print sheet made of an iron plate or the like. SOLUTION: In this method for identifying a metallic plate print sheet 7 by detecting a color mark 8 attached to the metallic plate print sheet 7, spectral reflectance from the metallic plate print sheet 7 is measured with a spectroreflectometer (spectroreflectometer 13 with a projection angle of 0 degrees and a receiving angle of 45 degrees) which receives light beams reflected in diagonal directions other than vertical direction with respect to the sheet surface of the metallic plate print sheet 7, and chromaticity (chromaticity a* or b* on CIE-L*a*b* coordinates) is computed on the basis of the spectral reflectance measured. The chromaticity a* or b* obtained through computations is compared to a preset discriminating chromaticity threshold so as to determine whether or not the color mark 8 exists.