Patent ID: 6934226

Claim:
An optical disk apparatus comprising: an optical pickup comprising a laser source, a focusing optical system for receiving a light beam emitted from the laser source and focusing the light beam on an optical disk to form a tiny spot, a transfer system for transferring the focusing optical system in a direction substantially perpendicular to the optical disk, a photodetector for receiving light reflected from the optical disk and outputting an electric signal in accordance with a quantity of light, and an aberration correcting system for correcting spherical aberration of the focusing optical system; a focusing error detection device for detecting a focused state of the tiny spot on the optical disk based on the output signal from the photodetector; a focusing control device for controlling the focused state of the tiny spot on the optical disk so as to be a predetermined state by driving the transfer system based on an output signal from the focusing error detection device; a disk discrimination device for discriminating a type of the optical disk; and an aberration correction quantity switching device for switching a quantity of spherical aberration correction of the aberration correcting system selectively based on a signal from the disk discrimination device, wherein the aberration correcting system comprises a liquid crystal element, and the quantity of spherical aberration correction of the aberration correcting system is preset based on an output signal from the aberration correction quantity switching device before operating the focusing control device.