Device and method for use in optical record carrier systems

signal-processing device (301) for controlling a focus actuator (309) in an optical disc system (30), wherein the signal processing device (309) generates a focus actuator control signal (CS) to be supplied to the focus actuator (309). The focus actuator control signal (CS) is based on a focus error signal (FE) and a central aperture signal (CA). If the central aperture signal (CA) is equal to or above a certain threshold value the focus actuator control signal will correspond to the focus error signal (FE). However, when the central aperture signal is below the threshold value the focus actuator control signal will have a predefined level. By providing a focus actuator control signal (CS) in accordance herewith it is possible to extend the regions of the focus error signal (FE) in which the relative distance between the focus point and the data layer of the record medium (304) is not correctly represented. The provision of the control signal (CS) enables improvements of the start-up and recovery performance of optical disc systems, especially under vibrating conditions.