Patent ID: 8928948
Filing Date: 2015-01-06
Classification: B41M

Abstract:
1. A computer-implemented method of encoding infrared security watermarks with a set of printing devices, the method comprising: choosing a set of colors that lies within a common gamut of the set of printing devices and is defined within a device-independent color space, wherein input colors are related to output physical colorant combinations using transformation tables and interpolation between measured values; for each color in the set of colors and for each printing device in the set of printing devices, obtaining a metameric pair of device colorant values corresponding to minimum and maximum black (K) values is selected; processing the metameric pair sets to extract a smaller subset of colorant values that satisfies a given set of criteria; storing data associated with the smaller subset of colorant values that satisfies a given set of criteria in resource files in a database that link fixed device-independent infrared color names to pairs of variable device-dependent colorant values, the data having two distinctly named entries that refer to the same color bit in Lab color space to two different colorant combinations having a differential IR response; and using at least one of the printing devices and the stored data to generate an infrared readable text.