PURPOSE: To narrow the track pitch and to enhance the recording density and then to highly speed up the read of data by irradiating over two tracks with a light beam spot.
CONSTITUTION: Scanning is performed when the center of the beam spot SP is positioned at a middle point between the tracks as under the just tracking state. A middle position between the tracks is irradiated by the spot SP. By this method, information by pots P on the tracks TK n and TK n+1 can be read out by scanning them in one revolution. As a result, the data read-out speed is approximately doubled.