| 摘要 |
PURPOSE:To enable measuring a size or a built-in location of a magnetic card etc. with a structure composing of a magnetic tape built-in at the inside of a card exactly by detecting a difference of the transmissivity for a designated electromagnetic wave between a magnetic tape and a raw material of a card. CONSTITUTION:An infrared ray emitted from a light source 3 is made incident to a reflecting mirror 5 after passing through a pin hole 4 and is irradiated to a range S including a magnetic card 1 to be inspected. A detector 10 outputs a level of electric signal in proportion to the strength of an infrared beam through a reflecting mirror 8 and inputs to a phase detector 12 through an amplifier 11. In the range S2 containing a magnetic tape 2, the infrared ray hardly penetrate, in the ranges S1, S3 of the only plastic material portion, approx. 10-30 % of the infrared ray penetrates and in the range of S4 composed of the air only, the infrared beam passes through perfectly. Therefore, exact information can be obtained not only on the card designed in color on its surface but also on the card containing a magnetic tape built-in at the inside of the card.
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