US Patent 7965862 Method to apply an invisible mark on a media

The present application aims to propose a solution for embedding invisible mark suitable for very large production volumes. This is achieved by a method for applying an invisible mark on a media based on a pattern, and comprising the following steps: determining an area to apply this mark, applying a transparent or semi-transparent substance, on the media, said substance being modulated with the active dots to form the pattern by modifying the quantity of the substance at each active dot.