Detection and deterrence of counterfeiting permits one to make legitimate color copies without introducing visual artifacts or experiencing substantial processing delays. We enable an efficient counterfeit deterrence by the use of an hierarchic detection scheme, in which the majority of documents are...http://www.google.co.uk/patents/US6516078?utm_source=gb-gplus-sharePatent US6516078 - Multi-level detection and deterrence of counterfeiting of documents with reduced false detection
