Two or more digital watermarks are embedded in an identification document. In one implementation the digital watermarks include characteristics that are chosen so that the watermarks will be affected in different manners if the identification document is subsequently copied or reproduced. The detection...http://www.google.fr/patents/US20050058320?utm_source=gb-gplus-shareBrevet US20050058320 - Identification document including multiple watermarks
Identification document including multiple watermarks
Numéro de demande: 10/858,820 Numéro de publication: US 2005/0058320 A1 Date de dépôt: 1 juin 2004 Brevet délivré: US7539325 ( Date de délivrance 26 mai 2009)
