Importance

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Abstract

A document containing security images which enable original documents to be distinguished from copies of the originals. The document may include a background of a first color and an image formed of a second and third color which appear to be the first color when viewed together, providing a hidden image which does not appear in reproductions of the document. The document may contain a background of a first color printed with lines at a first angle, and an image of the first color but having lines printed at a different angle, providing a hidden image which does not appear in reproductions of the document. The document may contain a background of printed with lines at a first angle and a predetermined line frequency, and an image printed with lines at a second angle and at a line frequency less the one half of the line frequency of the background, providing a substantially hidden image which appears in a reproduction of the document. A document may be authenticated as an original document by detecting the presence of a predetermined hidden security image and/or by determining the layout of the document to be the same as the expected layout of an original document

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First Claim