Patent ID: 7239583
Filing Date: 2007-07-03
Classification: G11B

Abstract:
1. A tracking error detection apparatus comprising: a photodetector comprising four photoreceptor elements which are partitioned along a tangential direction and a perpendicular direction with respect to an information track that is recorded as an information pit line on a recording medium; zerocross detection circuits for detecting zerocross points at which two digital signals intersect center levels of the respective digital signals, each of said two digital signals being obtained by adding output signals from the two photoreceptor elements positioned on a diagonal line, among four signals that are generated according to the amounts of received by the respective photoreceptor elements and are outputted from the photodetector; a phase difference detection circuit for performing phase comparison based on a distance between the zerocross points of the two digital signals, and outputting a result of phase comparison obtained between the respective zerocross points as a pulse signal having a pulse width corresponding to one period of a sampling clock; and a low-pass filter for performing band restriction to a signal outputted from the phase difference detection circuit to obtain a tracking error signal.