| 摘要 |
PROBLEM TO BE SOLVED: To effectively prevent illegal copies of optical disks recorded with music software and game software, etc. SOLUTION: A low density bar code symbols 5 and 5' and high density bar code symbols 6 are constituted by bar code elements formed as through holes in a radial pattern in a specular surface area 4 on the innermost circumferential side of the optical disk, and the high density bar code symbols 6 constitute a logotype part 7 by two-dimensionally arranging the plural symbols 6. The symbols 5 and 5' and the symbols 6 are shown as information of the same contents for discriminating the optical disk or information for obtaining identification information of the optical disk in a certain arithmetic algorithm by using both bar code symbols. When the identification information of the optical disk is obtained by confirming either of the symbols to be reasonable information and coincidence between the two symbols in their information in the former case, or by calculating the algorithm in the latter case, reproducing permission of main information of the optical disk is given as the legal disk by the reproducing device. |
