| 摘要 |
PURPOSE: To provide a double layered optical disk and an optical disk device suitable for reproducing two optical disks different in thickness. CONSTITUTION: A lead-in groove 101 of one recording surface of the double layered optical disk is arranged on the inner peripheral side and a lead-out groove 102 is arranged on the outer peripheral side, meanwhile a lead-in groove 111 of another recording surface is arranged on the outer peripheral side and a lead-out groove 112 is arranged on the inner peripheral side. The optimum thickness of optical disk substrate when looked from an objective lens used for an optical pickup of the optical disk device is set to (a)<(t)<(a+b), where (a) is the thickness of a 1st substrate 2, (b) is the thickness of a 2nd substrate 3, (t) is optimum thickness of a substrate looked from objective lens. |
