| 摘要 |
PURPOSE: To facilitate discrimination of whether it is a regular optical disk or not by comparing rotational period of a part different in recording transfer rate with rotational period of a part of other usual recording transfer rate. CONSTITUTION: When the optical disk is a CD-ROM, a pickup part 4 is sought by a prescribed address of a usual track based on information in a storage part 11, and the rotational period of disk of one revolution in the part is measured. Then, the pickup 4 is sought by the address between the addresses of the track on which information is recorded at a low recording transfer rate, and the rotational period of the optical disk is measured. Then, the change rate of the rotational period is obtained in a comparison part 13, and when the change rate is smaller than a prescribed setting value H, a control part 10 recognizes it as a regular disk, and when the change rate is larger than the setting value H, the control part 10 recognizes it as an irregular disk, and performs copy prevention action such as disk ejection operation, etc. |
