| 摘要 |
<p>PURPOSE:To judge the justifiability of a card by forming a pattern recording part in which card inherent data is preliminarily entered by a non-linear optical substance absorbing laser beam having a specific wavelength and generating higher harmonics. CONSTITUTION:A pattern recording part 2 in which bar code like card inherent data is entered by ink containing a non-linear optical substance generating higher harmonics by the irradiation with laser beam is formed to the surface of a card 1. A card is charged to accelerate the generation of higher harmonics of the pattern recording part 2 by a laser beam irradiation means and the card inherent data is read by an optical reading means to be compared with reference data by a comparing and collating means S2 and, only when both of them coincide, the card is judged to be correct. As the non-linear optical material constituting the ink composition of the bar code like recording part, there are two kinds of inorg. and org. ones and lithium niobate or lithium iodate is used as the inorg. one and urea or 3-methyl-4-nitropyridine-1-oxide is used as the org. one. The non-linear optical substance absorbs laser beam to generate higher harmonics.</p> |
