Track retrieving method for making a light beam jump and scan from one

Abstract

A track retrieving method for making a light beam shift to a target track is provided in an apparatus in which at least one of a writing operation and a reading operation of information is performed to an information medium. A tracking control is applied to the information medium so as to make the light beam position on track. The information medium has tracks such that the polarity of the tracking control is alternately inverted between tracks. The method includes the steps of: making the light beam shift toward the target track, after the tracking control is made non-operational; and detecting a tracking error between the light beam and the track. The method also includes: generating a tracking error signal corresponding to the tracking error; generating a track middle-point signal for detecting a middle-point between adjacent tracks of the information medium based on a change of a polarity of a differentiation signal obtained by differentiating the tracking error signal; and generating a deceleration pulse for decelerating a shift of the light beam according to the track middle-point signal. The method also includes the steps of inverting the polarity of the tracking control before the deceleration pulse is completed, and again operating the tracking control, after the deceleration pulse is completed, to make the light beam position on the target track.