Patent ID: 8085438
Filing Date: 2011-12-27
Classification: B41M

Abstract:
1. A method for producing a fluorescent halftone color image which is invisible under daylight and visible under UV light, using fluorescent inks and superpositions of fluorescent inks as fluorescent emissive colorants, the method comprising the steps of (a) selecting a set of at least two fluorescent inks and superpositions of said fluorescent inks as base fluorescent emissive colorants invisible under daylight; (b) by relying on emission spectra of said fluorescent emissive colorants, determining, using a color prediction model, under ultraviolet illumination the gamut produced by juxtaposed halftones of said fluorescent emissive colorants in a colorimetric space, and with said color prediction model creating correspondences between emitted colorimetric values and surface coverages of said fluorescent emissive colorants; (c) obtaining gamut mapped input image colors located inside the gamut formed by said fluorescent emissive colorants by gamut mapping of said input image colors into said gamut; (d) converting said gamut mapped input image colors into colorant surface coverages using said correspondences between said emitted device-independent colorimetric values and said fluorescent emissive colorant surface coverages; and (e) creating fluorescent color screens invisible under daylight according to said colorant surface coverages by juxtaposed halftoning,