| 摘要 |
PROBLEM TO BE SOLVED: To actualize an optical disk which can have its rotating speed accurately controlled and can have its preformat information accurately detected even when the track pitch is narrow. SOLUTION: Positions on grooves 1, where a synchronous mark 3 formed on the optical disk for detecting a synchronous signal which controls the rotating speed of the disk and a pre-mark 4 for detecting the preformat information including address information for position retrieval are displayed, are displaced from the position of the center line to the side of one land 2. Further, the synchronous mark 3 is made shorter than the pre-mark 4. Otherwise, the grooves 1 as the synchronous mark 3 and pre-mark 4 are displaced toward the respectively different lands 2. In this case, the displacement quantity of the synchronous mark 3 and pre-mark 4 is <=1/4 times as large as track pitch intervals. |
