Patent ID: 7719931

Claim:
An optical disk device for recording information in a first region and a second region of an information carrier having two or more regions of different track pitch, or for reproducing information that has been recorded, the first region being formed with a track pitch different from a track pitch of the second region, said optical disk device comprising: a focusing unit operable to focus an optical beam and direct the optical beam at the information carrier; a movement unit operable to move the focal point of the optical beam focused by the focusing unit in a radial direction of the information carrier; a light receiving unit operable to receive the optical beam reflected by an information side of the information carrier; a track offset detection unit operable to detect offset between the track and the focal point of the optical beam on the basis of a signal from the light receiving unit; a tracking control unit operable to drive the movement unit on the basis of a signal from the track offset detection unit, and to control the focal point of the optical beam so as to scan the track; a loop gain adjustment unit operable to adjust a first loop gain used in tracking control of the first region, which is the loop gain of the tracking control unit; and a loop gain estimation unit operable to estimate a second loop gain used in tracking control of the second region, wherein the loop gain estimation unit (i) detects, from the signal from the track offset detection unit, a first amplitude that is an amplitude of the signal from the first region and a second amplitude that is an amplitude of the signal from the second region, and (ii) estimates the second loop gain of the second region on the basis of the first loop gain of the first region determined by the loop gain adjustment unit and a ratio between the first amplitude and the second amplitude.