| 摘要 |
PURPOSE:To irradiate an optical disk with an optical beam by an optimal optical characteristic even at the time of recording and reproducing an optical disks whose thickness or refractive indexes are different from each other. CONSTITUTION:Compensating plates 10 for compensating the change of the optical characteristic accompanied with the change of the thickness refractive index of a substrate 2 of a disk 1, is interposed between the disk 1 and an objective lens 5. The plural compensating plates 10 are provided on the same circumference of a disk (revolver) 12, and each has the different thickness and refractive index. The revolver 12 is rotated by a motor 15, and one of the plural compensating plates 10a-10e is positioned between the objective lens 5 and the disk 1. |
