Abstract: An optical storage medium having land tracks and groove tracks alternately formed and capable of recording and reproducing information with respect to the land tracks and the groove tracks. The optical storage medium includes a plurality of first headers respectively having first track addresses as consecutive numbers given to the land tracks, and a plurality of second headers respectively having second track addresses as consecutive numbers given to the groove tracks independently of the consecutive numbers of the land tracks.

Abstract: On the assumption that a phase difference caused by a birefringence at the substrate is &phgr;br while a one caused by the magneto-optic Kerr effect of the recording layer is &phgr;MO, the magneto-optical recording medium formatted to record information in the groove meets the conditions: −20°<&phgr;br<+10° and −45°<(&phgr;br+&phgr;MO)<+15°, the magneto-optical recording medium formatted to record information on the land meets the conditions: −20°<&phgr;br<+10° and −15°<(&phgr;br+&phgr;MO)<+45°, and the magneto-optical recording medium formatted to record information at both the land and groove meets the conditions: −20°<&phgr;br<+10° and −15°<(&phgr;br+&phgr;MO)<+15°.

Abstract: A magneto-optical recording system which is compatible the write-after-erase magneto-optical media and the directly-over-write magneto-optical media. The magneto-optical recording system provided by the present invention includes a detector used for detecting the type of the medium and a controller coupled to the detector and controlling a write-after-erase operation or a direct-over-write operation with respect to the medium responsive to the medium type.

Abstract: Marks are recorded on an optical disk which is rotated at a constant rotational speed by laser light which is converged on a substantially circular spot. The pulse width of a recording pulse is set at a sufficiently narrow value and the recording power of the laser light is maintained at a constant value. Marks (corresponding to "1") are recorded on the entire disk surface by the laser light with the same recording pulse width and with the same recording power. The recording pulse width is less than about 30% of the mark interval obtained when they are recorded on the optical disk at the highest density. The recording power is set at the value which produces the maximum reproduction amplitude when said marks are recorded on the optical disk at the highest density.