| 摘要 |
<p>Drawing lines (2) constituting a line drawing consists of a basic line portion and a broken line portion. A plurality of basic line portions (5) are gathered into a basic line group constituting a background portion (4) while a plurality of broken line portions (1) are gathered into a broken line group constituting an image portion (3). From the background portion (4) and the image portion (3), information is embedded. The broken line portion (1) consists of a plurality of broken lines (6) each extending in the direction vertical to the longitudinal direction of the drawing lines (2) and arranged at a predetermined interval. It is difficult to recognize the embedded information under visible light by the naked eye. However, the embedded information can easily be detected by a read device such as a scanner. By performing the Fourier transform, extraction of particular frequency, the inverse Fourier transform, and the like, it is possible to easily authenticate a printed sheet with a high accuracy.</p> |
