Patent ID: 7133343

Claim:
An optical disk apparatus comprising: a phase converter for converting a transfer phase of a light beam component of a light beam irradiated from a light source, the light beam including a first light beam component being away from an optical axis center in the direction perpendicular to the optical axis by a predetermined range and a second light beam component being within the predetermined range from the optical axis center in the direction perpendicular to the optical axis, the phase converter converting the transfer phase of the second light beam component; an objective lens including a first condensing lens and a second condensing lens, the first condensing lens condensing the light beam including the second light beam component phase-converted by the phase converter, the second condensing lens condensing the light beam condensed by the first condensing lens; an objective lens holder which holds said objective lens and is supported to be drivable in an optical axis direction of said objective lens and in one direction perpendicular to the optical axis; a focusing actuator for driving said objective lens holder in the optical axis direction; first focus detection means for detecting a deviation in the optical axis direction on the basis of reflected light of the first light beam component focused at a first numerical aperture of the light beam focused by said objective lens; second focus detection means for detecting a deviation in the optical axis direction on the basis of reflected light of the second light beam component focused at a second numerical aperture lower than the first numerical aperture of the light beam focused by said objective lens; addition means for adding a second focus error signal detected by said second focus detection means to a first focus error signal detected by said first focus detection means; and drive control means for driving said focusing actuator in accordance with an output from said addition means, wherein the first condensing lens condenses the first light beam component without condensing the second light beam component by using a phase difference between the first and second light beam components, and the second condensing lens condenses the first and second light beam components, wherein said first focus detection means detects the first focus error signal on the basis of the reflected light of the first light beam component that forms a first optical spot with a first spot size on an information recording surface of an optical disk and wherein said second focus detection means detects the second focus error signal on the basis of the reflected light of the second light beam component that forms a second optical spot with a second spot size larger than the first spot size on the information recording surface of the optical disk.