Patent ID: 8310908

Claim:
A spherical aberration correction appropriate position search apparatus, comprising: a spherical aberration correction device movement control device configured to control movement of a spherical aberration correction device for correcting spherical aberration of an object lens which collects a laser on an optical disc by moving toward or away from the object lens; a focus error amplitude obtaining device configured to obtain amplitudes of a focus error signal indicating a distance between a focal point of the laser by the object lens and a signal recording surface of the optical disc; an error amplitude difference calculation device configured to calculate an error amplitude difference which is a difference between the amplitudes of the focus error signal obtained by the focus error amplitude obtaining device at two different positions in a moving range of the spherical aberration correction device; and an appropriate position search control device in charge of overall control of the spherical aberration correction device movement control device, the focus error amplitude obtaining device, and the error amplitude difference calculation device, wherein the appropriate position search control device decides an appropriate position of the spherical aberration correction device based on the error amplitude difference.