Patent ID: 7948839

Claim:
An optical disk apparatus comprising: an optical pickup unit for reading out information recorded on an optical disk; a demodulation circuit for demodulating digital data from an output signal of the optical pickup unit; and a controller for performing a servo control based on the output signal of the optical pickup unit, wherein, when performing a focus/tracking control in a recess and a protrusion of a guide groove of the optical disk, the controller obtains a focus control circuit gain difference between the recess and the protrusion by comparing focus offsets with respect to variations in amplitudes of signals from the optical disk for the recess and the protrusion, respectively, wherein a focus control circuit gain Gg for the recess is set as: Gg=Gl −20*log(Δ Vg/ΔVl ) wherein Gl is a focus control circuit gain for the protrusion; and ΔVg and ΔVl are focus offset widths in the recess and the protrusion, respectively, each width representing a range within which an amplitude of each signal from the optical disk reduces from a maximum level to a specific level.