To equalize signal strength from necessary format information by forming, in a format information group, an irregular pattern synchronized with the irregular pattern formed in a format information land, in a manner linked continuously in the radial direction.
The irregular pattern formed in a format information group by the irradiation of a second laser beam is synchronized with the irregular pattern formed in the adjacent inner circumferential format information land by the irradiation of a first laser beam. From this, it is possible that the irregular pattern of control information and address information formed in the format information group and those formed in the format information land are nearly perfectly synchronized with each other, and that the irregular pattern is formed in a manner linked continuously in the radial direction. Thus, format information can be recognized while an optical head is made to seek between tracks.
KAWASAKI TATSUO
HIRAMATSU SHIGERU
