Patent ID: 8498187

Claim:
An optical disk apparatus for reproducing information from an optical disk, or recording information on the optical disk by using laser light, comprising: an objective lens which collects the laser light; an actuator which drives the objective lens; a detector which detects reflection light from the optical disk; a focusing error signal producing means which produces a focusing error signal (FES) from the reflection light detected by the detector; a spherical aberration correcting element which corrects spherical aberration occurred in the laser light; a control module which produces and outputs a focusing drive signal (FDS) for controlling the actuator and a spherical aberration correcting element drive signal for controlling the spherical aberration correcting element; an actuator driving means which amplifies the focusing drive signal (FDS) to supply electric power to the actuator; and a spherical aberration correcting element driving means which receives the spherical aberration correcting element drive signal to change a spherical aberration correction amount of the spherical aberration correcting element; wherein, in the case that the control module discriminates the optical disk having information recording planes, a total layer number of which is equal to or larger than a predetermined layer number, the control module performs a sweep process for moving the objective lens along a focusing direction a plurality of times while the spherical aberration correction amount of the spherical aberration correcting element is changed, wherein, when the control module discriminates that the information recording planes of the optical disk are two or more layers in a first sweep process, the control module changes the correction amount of the spherical aberration correcting element is changed, and then a second sweep process; and when the control module discriminates that the information recording plane of the optical disk is a one layer in the first sweep process, the control module discriminates the optical disk based upon the first sweep process.