| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a paper document having invisible discrimination information which authenticates an original. <P>SOLUTION: Partial pixel values of a specific halftone pattern are changed to generate a marking pattern representative of a bit value of discrimination data, and the marking pattern is printed over an original image of a document. For example, a precise pattern of 150 or more lines is given as the halftone pattern. When the paper document having the marking pattern printed thereon is copied, the marking pattern is substituted for a similar pattern by ambiguity of analog conversion. At this time, discrimination data which the marking pattern has is lost. Discrimination data cannot be detected from a copy of the paper document. Consequently, the paper document is determined to be an original or a copy in accordance with whether discrimination data can be detected. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
