Optical disc system and optical disk therefor
 An optical disc system using an optical disc with a light-transmitting cover and an objective lens for bundling or focusing a laser beam on a recording layer of the optical disc in order to perform recording and/or reproduction. The thickness t.sub.2 of the light-transmitting cover is set to fall within the range of 0.6 to 0.1 mm, the numerical aperture (NA) of the objective lens is set to fall within the range of 0.55 to 0.70 and the wavelength of the light beam is selected to be between 635 and 650 nanometers. 
Sony Corporation
G G G G G G G G G G G G G G
G11B G11B G11B G11B G11B G11B G11B G11B G11B G11B G11B G11B G11B G11B
inventional inventional inventional inventional inventional inventional inventional additional inventional inventional inventional inventional inventional inventional
Tetsu Yoshio
Watanabe Aoki