Patent ID: 7035177

Claim:
An apparatus for correcting aberration occurring in recording/reproducing information into or from a track of an optical recording medium on the basis of reflected light of a light beam irradiating the optical recording medium, comprising: an objective lens for converging the light beam; an actuator for three-dimensionally moving the objective lens; and an aberration correcting unit receiving the reflected light, for correcting aberration, said aberration correcting unit comprising: a photodetector receiving the reflected light so that the reflected light is divided along a direction corresponding to a track width direction and a direction crossing the track width direction, for calculating a first aberration derived from a tilt along the track width direction and a second aberration derived from a tilt along the direction crossing the track width direction, based on brightness of reflected light received in an arbitrary timing correspondingly to a diffraction pattern peculiar to the first aberration and to a diffraction pattern peculiar to the second aberration respectively, and for outputting detection signals of the first aberration and the second aberration; a tilt control unit receiving the detection signals, for correcting the tilt along the track width direction and the tilt along the direction crossing the track width direction on the basis of the detection signals; wherein at least one photodetector includes, on a light receiving surface thereof, a first light receiving area formed on one side along the track width direction in the reflected light and a second light receiving area formed on the other side, each of the first and second light receiving areas being divided into a center area and an edge area relative to the light receiving surface, each of the center and edge areas being divided into two areas along the direction crossing the track width direction.