Patent ID: 7545707

Claim:
An optical disc drive comprising: a carriage faced to a surface of an optical disc movably in a radial direction of the disc; a first actuator for driving the carriage; a light source for generating a laser beam; an objective lens supported on the carriage movably in radial directions of the disc for formation and placement of a beam spot formed from the laser beam generated by the light source onto the optical disc for recording or reproducing information on a plurality of centric or spiral tracks in the optical disc; a second actuator for moving the objective lens; a first signal generator for generating, upon a crossing movement by the beam spot over the track in the optical disc, a first signal based on a reflected beam from the optical disc and having a sine-wave amplitude pattern representing the crossing movement of the beam spot over the track; a second signal generator for generating a second signal based on an amplitude change of the first signal generated by the first signal generator, as a square wave signal reversing its level upon each crossing movement of the beam spot over the track; a first speed calculator for calculating a traveling speed of the carriage during a seek operation by the carriage; a second speed calculator for calculating a traveling speed of the objective lens based on the second signal during the seek operation by the carriage; a controller for controlling the second actuator for a movement of the objective lens at a relative traveling speed of zero with respect to the carriage, based on the traveling speed of the carriage and the traveling speed of the objective lens calculated by the first and the second speed calculator; wherein the optical disc drive further comprises: a first position detector for detecting position information of the objective lens in the carriage right before starting of the seek operation by the carriage; a memory for storing the position information of the objective lens detected by the first position detector; a second position detector for detecting position information of the objective lens in the carriage at a predetermined time interval during the seek operation by the carriage; and a position corrector for comparing the position information detected by the second position detector to the position information stored in the memory, and for correcting a position of the objective lens in the carriage to a position indicated by the information stored in the memory upon an error between the two pieces of position information exceeding a predetermined threshold value.