| 摘要 |
PROBLEM TO BE SOLVED: To prevent forgery of an optical recording medium. SOLUTION: An optical recording medium 4 is composed of two recording areas M1 and M2 having their different reflectances, and information is optically recorded in these recording areas M1 and M2. Light sources (laser diodes) LD-1 and LD-2 are disposed in positions for irradiating the recording areas M1 and M2 with their laser beams of the same wavelength respectively, and rugged shapes of the recording areas M1 and M2 are scanned. The laser beams of the LD-1 and LD-2 reflected by the recording areas M1 and M2 are received by reading parts (photodetectors) PD-1 and PD-2 respectively, and whether or not both signal levels read out by the PD-1 and PD-2 exceed their individual thresholds is judged by a decoding part 3 to determine a genuine article or a forgery, and in the case of the genuine article, restoration to its original data is performed based on data read out by the PD-1 and PD-2 respectively. |
