| 摘要 |
PROBLEM TO BE SOLVED: To reduce the outside diameter of an optical disk and also to secure a large information recording area of the same. SOLUTION: The disk is provided with a central hole 16 and a reference surface 20 in the peripheral part of the central hole 16 for being positioned in a prescribed position and held by the disk rotation driving mechanism in the side of an optical disk device. The reference surface 20 is positioned and provided on the surface facing the irradiation surface 17 which is irradiated with laser beams from the optical pickup on the optical disk device side. |
