Patent ID: 7525884

Claim:
A position control apparatus, comprising: a position error signal detector that detects a position error signal of a mechanical part; a phase compensator, wherein the position error signal is supplied to said phase compensator to perform phase compensation thereon; a position controller that controls a position of the mechanical part based on the phase compensated position error signal from said phase compensator; a first switch connected between said phase compensator and said position controller, the first switch configured to be (1) turned off when a focus drive is off, (2) to be connected to the phase compensator, and (3) to be connected to a focus search signal; and a determination device that determines whether an absolute value of a focus error is smaller than a predetermined value and whether a pull-in signal value is greater than a threshold; wherein said first switch is (a) connected to the focus search signal when the determination device determines that the absolute value of the focus error is larger than the predetermined value and the pull-in signal value is less than the threshold and (b) is connected to the phase compensator when the determination device determines the absolute value of the focus error is smaller than the predetermined value and the pull-in signal value is greater than the threshold; an on/off second switch positioned between said position error signal detector and said phase compensator, and that is turned on to connect said position error signal detector to said phase compensator when the determination device determines the absolute value of the focus error is smaller than the predetermined value and the pull-in signal value is greater than the threshold.