| 摘要 |
PROBLEM TO BE SOLVED: To exclude influence of a reproducing error owing to dirt and a flaw on a recording surface and to judge the presence of only actual falsification as accurately as possible by operating exclusive-OR between regular recording information subjected to error correction and its inverted information. SOLUTION: The exclusive-OR operation is performed between the error corrected regular recording information and the inverted information in every one bit corresponding to each other. If the regular information and the inverted information have a completely inverted relationship to each other, a result of the exclusive-OR of each bit of them is every 1. On the other hand, if inverted relationship between the two bits of information is degenerated, a result of at least one exclusive-OR becomes 0. Then, whether the result of the exclusive-OR obtained in the previous step has 0 or not is examined. If not (NO), no falsification of the recording information is judged, and the error corrected regular recording information is outputted as reproducing data. On the other hand, if so (YES), falsification of the recording information is judged to be in existence. |
