Patent ID: 7200077

Claim:
A device for detecting a tilt angle of an optical recording medium recording/reproducing device provided with an optical system that guides a laser beam irradiated from a light source onto a recording surface of an optical recording medium, and receives at a light receiving portion the laser beam reflected by the recording surface of the optical recording medium, comprising: a photodetector provided at the light receiving portion, which has a light receiving surface divided into at least four segments along a track tangent direction of the optical recording medium and a direction that is perpendicular thereto, and which outputs light reception signals corresponding to an intensity of a laser beam received at the four segments of light receiving surface; a first push-pull signal generator which generates, as a first push-pull signal, a difference between the light reception signals of said photodetector corresponding to two light receiving surfaces of one side of the four light receiving surfaces, which are divided in the track tangent direction; a second push-pull signal generator which generates, as a second push-pull signal, a difference between the light reception signals of said photodetector corresponding to two light receiving surfaces of the other side of the four light receiving surfaces, which are divided in the track tangent direction; and a tilt signal generator which generates a tilt signal that indicates a tilt angle defined by a normal on the recording surface of said optical recording medium at a position of irradiation of the laser beam and the optical axis of the laser beam in accordance to a difference between an amplitude of the first push-pull signal and an amplitude of the second push-pull signal, wherein said tilt signal generator includes: a pattern identifying device which identifies whether or not a track pattern at a center position in which the laser beam is irradiated on the recording surface of said optical recording medium is a predetermined pattern; and a switching element which turns on to relay the tilt signal when the predetermined pattern is identified by said pattern identifying device.