Patent ID: 7499381

Claim:
An optical disk apparatus, comprising: an aberration correcting unit for correcting aberrations generated when laser beams are focused on a recording surface of an optical disk with a use of an objective lens; a servo signal generating unit for generating servo signals based on reflected signals sent from the optical disk and outputting the servo signals; a servo control unit for putting focused light spots on tracks of the optical disk by controlling a drive of the objective lens based on received servo signals; a birefringence detecting unit configured so that the birefringence detecting unit detects a degree of the birefringent portions on the recording surface based on the received servo signals and generates aberration correcting signals to correct the aberrations based on the degree of the birefringent portions detected and outputs the aberration correcting signals; the aberration correcting unit is configured to correct the aberrations based on the received correcting signals through driving prescribed aberration correcting elements; and the servo signal generating unit, when generating the servo signals using electric signals according to the reflected signals and predefined parameters, determines parameter values according to a degree of the aberration correction.