A document containing lines printed at an interference scanning frequency which causes conventional scanning and copying devices to introduce distortions in a copy of the document and prevents color separating copies of the document. The document bears an image which has lines printed at a line frequency...http://www.google.fr/patents/US20070133023?utm_source=gb-gplus-shareBrevet US20070133023 - Document For Determining Interference Scanning Frequencies
Document For Determining Interference Scanning Frequencies
