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

A magneto-optical disc system for recording information signals and/or reproducing information signals comprising:

• laser beam generating means for generating a laser beam;
• a magneto-optical having including a rigid light-transmitting substrate, a magneto-optical recording layer formed on the light-transmitting substrate and irradiated by the laser beam from said the laser beam generating means through the light-transmitting substrate during recording and reproduction, and a light-transmitting cover layer covering the magneto-optical recording layer and capable of transmitting the laser beam ;
• an objective lens for focusing the laser beam on the magneto-optical recording layer through said the light-transmitting cover layer substrate;
• and
• magnetic field applying means for applying a magnetic field to the magneto-optical recording layer,
• wherein said the magneto-optical disc system is characterized in that the thickness of the light-transmitting cover layer substrate of said the magneto-optical disc falls within a range of 0.6 to 1.0 0.1 mm, and a numerical aperture of said the objective lens falls within a range of 0.55 to 0.70.

A magneto-optical disc system for recording and/or reproducing information signals comprising:

• a magneto-optical disc including a rigid an interconnecting substrate having two sides, each side of said the interconnecting substrate having a magneto-optical recording layer formed thereon and a light-transmitting cover layer formed on said recording layer to cover said recording layer connected thereto;
• and
• a pair of magneto-optical pickup units arranged on opposite sides of said the magneto-optical disc so as to face each other with respect to the magneto-optical disc, each magneto-optical pickup unit includes:
• laser beam generating means for generating a laser beam to said the magneto-optical disc during recording and/or reproduction;
• an objective lens for focusing said the laser beam on said the magneto-optical recording layer through said the light-transmitting cover layer;
• magnetic field applying means arranged near said the objective lens to apply a magnetic field to said the magneto-optical recording layer;
• ,
• wherein the thickness of said the light-transmitting cover layer falls within a range of 0.6 to 1.0 0.1 mm, and the numerical aperture of said the objective lens falls within a range of 0.55 to 0.70.