METHOD FOR TRACKING THE INFORMATION TRACK OF AN OPTICAL DISC

摘要

A method of radially tracking the information track of a multi-layer optical record carrier is disclosed. The method comprises generating a push-pull tracking signal derived from the light of a main spot, a first side spot and a second side spot falling on an optical detector, wherein the main spot, the first side spot and the second side spot are formed by focusing a main radiation beam, a first side radiation beam and a second side radiation beam, respectively, taking into consideration the effect of a background spot resulting from reflections of the main spot from out-of-focus layers of the multi-layer optical record carrier. The method is useful for optical pick-up units used for multi-layer discs such as Blu-ray discs, HD-DVD and DVD.