Patent ID: 7616536

Claim:
An optical disc drive, comprising: an optical system for scanning an optical disc with a light beam, the optical system comprising an optical detector for receiving light reflected by the optical disc; a radial actuator for radially displacing a focal spot of the light beam; a control circuit having an input for receiving an output signal of said optical detector, and having an output for generating a control signal for said radial actuator; wherein said control circuit is capable of operating in at least a first operating mode wherein said control signal for said radial actuator is generated on the basis of a tracking error signal derived from wobble-induced signal components of said optical detector output signal; wherein said control circuit is capable of operating in at least a second operating mode wherein said control signal for said radial actuator is generated on the basis of a tracking error signal derived from data-induced signal components of said optical detector output signal; wherein said control circuit is adapted to monitor said optical detector output signal, and to operate in said first operating mode when said optical detector output signal indicates an unwritten track, and to operate in said second operating mode when said optical detector output signal indicates a written track; and wherein said control circuit is adapted to monitor the signal power of low-frequency signal components of said optical detector output signal, and to switch to said first operating mode when said measured signal power shows an increase by more than a predetermined amount, for instance when the time-derivative of said measured signal power exceeds a predetermined positive reference level, and to operate in said second operating mode when said measured signal power shows a drop by more than a predetermined amount, for instance when the time-derivative of said measured signal power exceeds a predetermined negative reference level.