Patent ID: 7420889

Claim:
A tracking control apparatus for an optical disc which has wobble grooves as tracks, comprising: a signal detection unit including an optical head to transmit a push-pull signal from an optical spot focused on the optical disc, a low pass filter connected to the optical head, the low-pass filter receiving the push-pull signal, removing a wobble signal from the push-pull signal, and outputting a tracking error signal, and a band-pass filter of a wobble signal band connected to the optical head, the band-pass filter receiving the push-pull signal and allowing the wobble signal from the push-pull signal to pass through; a speed calculation unit calculating, in a tracking-off state, a relative moving speed between the optical spot and the tracks, from (i) a zero-cross point cycle in the tracking error signal and (ii) a track pitch; a polarity judgment unit judging, by a polarity judgment, that the optical spot is on a land if a wobble signal amplitude value is equal to or lower than a predetermined value in vicinity of a zero-cross point; a moving direction judgment unit, when the relative moving speed is within a predetermined range and the polarity judgment unit has judged that the optical spot is on a land, judging a moving direction of the optical spot relative to the tracks, from a rise/decay direction of the tracking error signal; a control unit performing a tracking lead-in by reducing the relative moving speed, based on the relative moving speed calculated by the speed calculation unit and the moving direction, and the moving direction judgment unit judges whether the optical spot is moving from an inner circumference track toward an outer circumference track or from the outer circumference track toward the inner circumference track, according to whether a differential coefficient of the tracking error signal is positive or negative, wherein the polarity judgment unit includes at least one of: a first judgment sub-unit judging that the optical spot is on a groove if a RF signal amplitude value from the optical disc is equal to or higher than a predetermined value; a second judgment sub-unit judging whether the optical spot is on a groove or a land based on total light quantity signals from the groove and the land of the optical disc if there is a difference between the total light quantity signals; and a third judgment sub-unit judging whether the optical spot is on a groove or a land based on total light quantity signals from the groove and the land of the optical disc if there is a difference between the total light quantity signals, excluding portions of the optical disc for which the RF signal amplitude value from the optical disc is equal to or higher than the predetermined value, wherein the moving direction judgment unit further judges the moving direction of the optical spot relative to the tracks from the rise/decay direction of the tracking error signal if any of the first to third judgment sub-units judges by a polarity judgment whether the optical spot is on a groove or a land.