Information storage medium and method for detecting forgeries

Abstract

An information storage medium has a base portion and a code storage portion. The code storage portion is disposed on the base portion and contains an infrared absorber which absorbs substantially only infrared rays within a narrow wavelength band. If a real information storage medium is produced like that, subject mediums are judged real or not by a method includes the steps of emitting rays to the subject medium, receiving rays reflected from the subject medium, detecting a first reflectance at the peak absorption wavelength and a second reflectance at a comparison wavelength near the peak wavelength, and judging if the subject medium is real or not. The rays at the comparison wavelength are not very much absorbed by the absorber.

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