New postage stamp design with tone gradation in Infraredesign technology

This paper deals with the application of new steganographic methods in postagestamp printing technology with the goal of securing them against counterfeiting.Postage stamp designs are presented which contain double information in the visibleand in the infrared spectrum area. New methods include printing with processprinting inks that have a continuous response in the infrared area of the spectrum.The infrared Z image cannot be produced with conventional CMYK separationin such a way that the hidden picture does not show through when looking at theprint. This is the reason for introducing CMYKIR separation, with mathematicalrelations that respect printing ink characteristics in the RGB to CMYKIR systemconversion.A mathematical model with targeted separation characteristics is proposed, withseven independent variables. It has been created as the result of optimal regressionmodel developed on the basis of colour tone measuring for the visual and infraredspectrum. A technological procedure has been elaborated for producing and printingbased on such designs. It is possible to detect the infrared image with the helpof a device – the infrared ZRGB camera. Counterfeiting is impossible due to theirreversible conversion of the CMYKIR separation into the RGB system applied incontemporary scanners or cameras.