MAGNETO-OPTICAL DISK AND MAGNETO-OPTICAL DISK SYSTEM

摘要

Provided are a magneto-optical disc system and a magneto-optical disc which can be freely defocused and have good recording and reproduction.;In the present invention, a protective film is formed on the magneto-optical disk, and recording and reproduction are performed while sliding the magnetic head on the protective film.;At this time, the shape of the focusing instrument of the optical system (the depth of focus of the servo band or the objective lens) or the projection of the surface of the magneto-optical disk is set to satisfy the following expression (1).;h: height of protrusion on protective film surface (m);r: radius of protrusion on protective film surface (m); _mD : mass of magneto-optical disk (kg);m: mass of the magnetic head (kg);Vx: ship speed (m / s);fc: Servo band (Hz);y: depth of focus of the objective lens (㎛)