New Postage Stamp Design With Tone Gradation in Infrared Design Technology

Abstract

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