Patent ID: 8184518

Claim:
An optical disc apparatus for recording or reproducing data on or from a multilayered optical disc, comprising: a pickup unit for focusing a laser beam onto the optical disc through an objective lens, receiving a laser beam reflected on the optical disc and detecting a signal from the received laser beam; the pickup unit having the objective lens and an actuator for driving the objective lens in a predetermined direction so as to perform the focus position control and the tracking position control of the objective lens; learning means for detecting a focus error signal by switching the objective lens at plural objective lens shift positions in the focusing direction, performing a predetermined approximation with respect to an unbalance amount between a positive amplitude and a negative amplitude of each detected focus error signal, and obtaining the objective lens shift position that makes the unbalance amount of the focus error signal minimum; and wherein when the actuator performs a predetermined control of driving the objective lens in the focusing direction, the actuator causes the objective lens to move to a predetermined objective lens shift position in the tracking direction by a predetermined amount and the objective lens at the predetermined objective lens shift position to move in the focusing direction.