| 摘要 |
<p>PURPOSE: To prevent copy (forgery) of paper money or securities in a copying machine. CONSTITUTION: An optical semiconductor is preliminarily mixed in a document, whose forgery should be prevented, in a prescribed mixture ratio. When the document 2 is read, a microwave is radiated to the document 2 through a transmission antenna 12, and the reflected microwave is received through a reception antenna 13. A lamp 7 is lit, and a lamp carriage 6 is driven. The optical semiconductor in the document whose forgery should be prevented is excited by the lamp 7, and the microwave reflectivity is increased, and therefore, the microwave reception level is raised. When the lamp carriage 6 is returned to the origin thereafter, the lamp 7 is extinguished, but the microwave is continuously transmitted and received. Since the optical semiconductor in this document is in the non-excited state at this time, the microwave reflectivity far is low, and the reception level is reduced. Consequently, the reception level for lighting of the lamp 7 and that for extinction are compared with each other to discriminate whether copy of the document whose forgery should be prevented is tried or not.</p> |
