Patent Number: RE37,428

Title: Magneto-optical disk system with specified thickness for protective layer on the disk relative to the numerical aperture of the objective lens

Abstract: A magneto-optical disc system includes a magneto-optical disc with a light transmitting protective layer, an objective lens for bundling or focusing a laser beam onto a magnetic recording layer of the magneto-optical disc in order to perform recording and/or reproduction, and a magnetic field generating unit formed as a coil pattern on a transparent optical glass layer. In the magneto-optical disc system, the thickness t.sub.2 of the light-transmitting protective layer is set to fall within the range of 0.6 to .[.1.0.]. .Iadd.0.1 .Iaddend.mm and the numerical aperture of the objective lens is set to fall within the range of 0.55 to 0.70, so as to obtain high density recording and/or reproduction by permitting the lens to be quite close to the actual recording layer.

Inventors: Watanabe; Tetsu (Tokyo, JP), Aoki; Yoshio (Tokyo, JP)

Assignee: Sony Corporation

International Classification: G11B 11/105 (20060101); G11B 11/00 (20060101); G11B 7/0037 (20060101); G11B 7/125 (20060101); G11B 7/007 (20060101); G11B 7/135 (20060101); G11B 7/24 (20060101); G11B 7/00 (20060101); G11B 011/00 ()

Expiration Date: 10/30/2018