Patent ID: 6169715
Filing Date: 2001-01-02
Classification: G11B

Abstract:
A tilt detection device for detecting inclination of a recording surface of an optical disc having continuous tracks and first shifted pits and second shifted pits formed such that the first shifted pits and the second shifted pits are orthogonally displaced respectively to a first side and a second side of a track from the centerline of the track, the continuous track being located between the second and first shifted pits, said tilt detection device comprising: an optical head operable to record and reproduce signals by focusing a light spot onto the optical disc; a two-split photo detector operable to receive light reflected from the optical disc, said photo detector including first and second photo detecting elements oriented so that said two-split photo detector is divided in a direction parallel to the track; tracking control means for controlling the position of the light spot on the continuous track; off-track detecting means for detecting an off track amount of the light spot based on a reproduction signal obtained by said two-split photo detector from said optical head moving along the track relative to the first shifted pits and second shifted pits; and tilt detecting means for detecting, while the light spot is located substantially at the center of the track by the control of said tracking control means and off-track detecting means, inclination of the recording surface of the optical disc with respect to the optical axis of the light beam by comparing output signals from said first and second photo detecting elements, when reflected light from the continuous track is received by said two-split photo detector, to produce a push-pull signal which represents the inclination of the recording surface.