초록 ▼

A fluorescence-based correlation mark is included in a printed document by encoding the correlation mark as phase shifts in the yellow halftone image only of a printed color document. The correlation mark transparency key is likewise printed using only yellow colorant or can be printed in black or w

A fluorescence-based correlation mark is included in a printed document by encoding the correlation mark as phase shifts in the yellow halftone image only of a printed color document. The correlation mark transparency key is likewise printed using only yellow colorant or can be printed in black or with another colorant or mixture of colorants that will appear dark or black when subjected to UV illumination. UV illumination of the document without use of the transparency key, and use of the transparency key without UV illumination of the document are insufficient to reveal the fluorescence-based correlation mark. UV illumination of the document while the transparency key is overlaid with the document will allow the correlation mark to be perceived.

대표청구항 ▼

The invention claimed is: 1. A method for authenticating a printed color document, said method comprising:illuminating the printed color document with a UV light source to emphasize a portion of the image printed using yellow colorant while the printed color document is overlaid with a transparency

The invention claimed is: 1. A method for authenticating a printed color document, said method comprising:illuminating the printed color document with a UV light source to emphasize a portion of the image printed using yellow colorant while the printed color document is overlaid with a transparency key so that both said transparency key and said printed color document are simultaneously illuminated by said UV light source, said transparency key including a transparency key halftone pattern printed thereon; and,observing through said transparency key any correlation marks embedded said portion of said image printed using yellow colorant while said transparency key and printed color document are simultaneously illuminated by said UV light source.