PURPOSE: To stably trace a track by setting a pit pattern with the aid of directional phase pits where positions equally spaced in the rotating direction of a guide groove are delayed with time at every track and other bits installed between guide grooves sandwitched by the directional phase pits.
CONSTITUTION: The guide groove 1 is cut in a head area to provide a mirror surface part 5. By delaying with time the cut position at every track, adjacent guide parts facing the mirror surface part 5 are of a depth of λ/4 to improve sensitivity for detecting a track deviation. A central bit 7 with a long pit is formed between the guide grooves sandwitched by a λ/4 pit part 6. A track offset caused between grooves by the inclination, etc., of a recording medium is removed when information is optically recorded and reproduced, whereby a track can be stably traced.
MAEDA TAKESHI
SHIGEMATSU KAZUO
TSUNODA YOSHITO
