Hiding patterns with daylight fluorescent inks

摘要

We propose a method for hiding patterns within printedrnimages by making use of classical and of two daylightrnfluorescent magenta and yellow inks. Under the D65 illuminantrnwe establish in the CIELAB space the gamut of a classicalrncmyk printer and the gamut of the same printer using arncombination of classical inks with daylight fluorescent inks.rnThese gamuts show that a significant part of the classical inkrngamut can be reproduced by combining classical inks withrndaylight fluorescent inks. By printing parts of images with arncombination of classical and daylight fluorescent inks insteadrnof using classical inks only, we can hide security patternsrnwithin printed images. Under normal daylight, we do not seernany difference between the parts printed with classical inksrnonly and the parts printed with daylight fluorescent inks andrnclassical inks. By changing the illumination, e.g. by viewing thernprinted image under a tungsten lamp or under a UV lamp, therndaylight fluorescent inks change their colors and reveal thernsecurity pattern formed by combinations of classical inks andrnof daylight fluorescent inks.