Apparatus for recording information on and/or reproducing information from optical disc including focus servo initialization using wobble pits

A focus servo apparatus for focusing a light beam from a light beam source to an optical disc having a plurality of pairs of wobble pits disposed one on each side of the center of a track on the optical disc and spaced from each other along the track, said focus servo apparatus comprising:

• an objective lens for converging the light beam onto the optical disc;
• an actuator for moving said objective lens along an optical axis thereof to apply the light beam in a focused condition to the optical disc;
• light detecting means for detecting a light beam returning from the optical disc when the light beam is applied from the light beam source through said objective lens to the optical disc;
• focus error detecting means for producing a focus error signal indicative of a deviation of the convergent light beam from a focused condition thereof on the optical disc, based on the light beam detected by said light detecting means;
• focus servo means for controlling said actuator to move said objective lens along the optical axis based on the focus error signal produced by said focus error detecting means;
• arithmetic means for calculating the average of peak values of the light beam detected by said light detecting means when the light beam returns from the respective wobble pits;
• and
• control means for adding a bias which maximizes the absolute value of said average calculated by said arithmetic means, to the focus error signal from said focus error detecting means, thereby producing a sum signal, and for controlling said actuator to move said objective lens based on said sum signal.