Patent ID: 7542381

Claim:
A method for driving a track counting device in a scanning unit for optical recording media in which data are stored in tracks and the position of the tracks transversely with respect to the track direction is modulated in a manner dependent on the position along the track in a predetermined manner, the scanning unit focusing a scanning beam onto the recording medium and evaluating the scanning beam reflected from the recording medium by means of a plurality of photodetector segments arranged adjacent, and deriving a track error signal from the difference between the signals of the left-hand photodetector segments in the track direction and the signals of the right-hand photodetector segments in the track direction; comprising the steps of: determining a wobble signal from the difference between a lower and an upper envelope of a track error signal that has been high-pass-filtered with a first cutoff frequency; determining a track zero crossing signal from a track error signal that has been low-pass-filtered with a second cutoff frequency; jointly evaluating the wobble signal and the track zero crossing signal in such a away as to ascertain whether, in the event of the sign changes of one signal, the respective other signal has positive or negative values; determining, from the result of the joint evaluation, drive signals that are used to drive a sequential logic for track counting.