Patent ID: 7764582

Claim:
A focus servo apparatus which performs a focus search operation of moving a focus position of laser light into a focus servo area, wherein the laser light is directed to a signal layer of a signal recording medium from an optical pickup apparatus having an objective lens actuator for driving an objective lens along a focusing direction, wherein the optical pickup apparatus has a power lens that changes an incidence angle of laser light incident on the objective lens and a power lens actuator that drives the power lens along an optical axis direction of the power lens, wherein, in the focus search operation, the focus servo apparatus controls the power lens actuator to drive the power lens along the optical axis direction while controlling the objective lens to remain in place, and wherein, upon detecting that the focus position has been brought into the focus servo area on the basis of a focus error signal obtained based on photo-reception outputs of a photo-detector of the optical pickup apparatus, the focus servo apparatus allows a focus servo to be in a lock state and returns the power lens to an initial position of the power lens while driving the objective lens so as to maintain the lock state, the power lens being an aberration correction lens that corrects spherical aberration caused by an output optical system of the optical pickup apparatus which directs the laser light to the signal recording medium, and the focus servo apparatus being configured to switch from driving the aberration correction lens according to the focus search operation to driving the aberration correction lens according to a spherical aberration correction signal for adjusting an amount by which to correct the spherical aberration by displacing the aberration correction lens along the optical axis direction when the focus servo is in the lock state.