Patent ID: 7616539

Claim:
An optical disc apparatus for accessing a desired one of a plurality of tracks on an optical disc, comprising: an optical head including: a light source operable to emit a light beam; a focusing lens operable to focus the light beam onto the optical disc; a photodetector having a plurality of light receiving areas and operable to successively receive the light beam reflected from the optical disc; and a lens drive operable to move the focusing lens along a radial direction of the optical disc, in accordance with input to the lens drive; an optical head driving unit operable to move the optical head along the radial direction of the optical disc, in accordance with input to the optical head driving unit; a measurement signal generating unit operable to generate measurement signals each indicative of a time-varying amount of light received on a respective one of the light receiving areas, the light being the light beam emitted by the optical head and reflected from different radial positions on the optical disc being rotated; a correction value determining unit operable, before tracking control, to (i) sequentially input, to the lens drive, preset values each determined in advance for moving the focusing lens, thereby causing the focusing lens to be sequentially moved in accordance with the preset values to a plurality of positions along the radial direction of the optical disc, and (ii) determine a correction value based on a difference between measurement signals in terms of predetermined low- and high-frequency components, the measurement signals being generated by the measurement signal generating unit as a result that the focusing lens is sequentially moved in accordance with the respective preset values; and a tracking control unit operable to perform tracking control after the correction value determining unit determines the correction value, by inputting to the lens drive unit a sum of the determined correction value and a control value determined for moving the focusing lens to a position corresponding to the desired track.