Patent ID: 7760599

Claim:
An optical disk apparatus, comprising: a spindle motor to mount an optical disk thereon, for rotational driving thereof; a pickup movable into a radial direction of the optical disk being rotationally driven by said spindle motor; rotation speed control means for controlling a rotation speed of said spindle motor; pickup movement controller means for controlling movement of said pickup, thereby recording/reproducing information through irradiating a laser beam upon an information recording surface of the optical disk; a signal generator portion for generating at least a tracking error signal and a lens shift indication signal upon reflected light of the laser beam irradiated from said pickup; and a signal process portion for controlling said rotation speed control means and said pickup movement controller means, upon basis of the tracking error signal and the lens shift indication signal from said signal generator portion, wherein said signal process portion comprises a mass eccentricity detection mode, detecting a greatest value and a smallest value on a signal after conducting a band pass filter process upon said lens shift indication signal in a step response of said pickup, to be memorized, with using a predetermined high-frequency signal, in place of said tracking error signal, and by changing an offset thereof, when controlling the rotation speed after loading the optical disk, and thereafter, detecting a maximum value and a minimum value on a signal after conducting band pass filter process upon said lens shift indication signal obtained from said signal generator portion, when shifting the disk rotation speed to a high speed, and thereby determining on whether the disk rotation speed be shifted to the high speed or not, upon basis of a value obtained through comparison of said maximum value and said minimum value obtained with said greatest value and said smallest value memorized.