Patent ID: 6510111
Filing Date: 2003-01-21
Classification: G11B

Abstract:
An apparatus for correcting aberration occurring in recording/reproducing information in or from tracks of an optical recording medium by using 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 part receiving the reflected light, for detecting aberrations derived from each of various causes and for correcting the respective causes, wherein the aberration correcting part includes: at least one photodetector which receives the reflected light dividedly along a direction corresponding to a track crosswise direction, and outputs aberration detection signals corresponding to the respective causes generated by calculating brightness of the divided light; and at least one controller selected from a tilt controller which receives a first aberration detection signal corresponding to a relative tilt between the optical recoding medium and the light beam and corrects the tilt on the basis of the first aberration detection signal, a thickness/focus controller which receives a second aberration detection signal corresponding to thickness variation of a substrate included in the optical recording medium and a focus error and corrects the thickness variation of the substrate and the focus error on the basis of the second aberration detection signal, and a tracking controller which receives a third aberration detection signal corresponding to a tracking error and corrects the tracking error on the basis of the third aberration detection signal, wherein at least one of the photodetectors includes, on a light receiving surface thereof, a first light receiving area formed on one side along the track crosswise direction 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, and the second aberration detection signal THES corresponding to thickness variation of the substrate and a focus error is calculated as follows: THES=((A1+B1)+k1)A3+B3))âˆ’k2((A2+B2)+k1(A4+B4)) wherein A1+B1 indicates brightness in the edge area of the first light receiving area; A3+B3 indicates brightness in the edge area of the second light receiving area; A2+B2 indicates brightness in the center area of the first light receiving area; A4+B4 indicates brightness in the center area of the second light receiving area; and k1 and k2 indicate real numbers.