Patent ID: 8194521

Claim:
An optical disc device for recording or reproducing information on or from a multilayer optical recording medium including a first recording layer and a second recording layer, the optical disc device comprising: an optical head including a light source, a condensing optical system including an objective lens for receiving a light beam emitted from the light source and forming a microspot on the multilayer optical recording medium, a photodetector for receiving the light beam reflected by the multilayer optical recording medium and outputting an electrical signal corresponding to the amount of light, a spherical aberration correcting portion for correcting a spherical aberration of the condensing optical system by changing a degree of divergence of light in the condensing optical system, and a coma aberration correcting portion for correcting a coma aberration of the condensing optical system; and a controller for controlling the condensing optical system, the spherical aberration correcting portion, and the coma aberration correcting portion, wherein the controller controls the condensing optical system and the coma aberration correcting portion so that the correction of the coma aberration from a value suitable for the first recording layer to a value specified for the second recording layer is started before a movement of a focus position of the microspot from the first recording layer to the second recording layer is completed, and wherein the controller substantially simultaneously starts the correction of the spherical aberration and the correction of the coma aberration.