OPTICAL INFORMATION RECORDING OR REPRODUCING APPARATUS

PROBLEM TO BE SOLVED: To solve a problem that in a method of detecting lens shift amounts using an observer with transfer characteristics equivalent to the optical pickup and correcting the offset of tracking error signal according to detected lens shift amount in conventional tracking control, an estimation error may arise by changing magnitude and phase of a tracking driving signal required for following eccentricity, and tracking control becomes unstable. SOLUTION: A memory means to store estimated displacement of an objective lens is provided, and when the rotational frequency of a disk is close to a primary resonance frequency, the stability of tracking control operation is raised by correcting the offset according to stored displacement of the objective lens and reducing the estimated error of the lens shift amount by fluctuation of the primary resonance frequency and the peak gain. COPYRIGHT: (C)2006,JPO&NCIPI