Scanning device with two-stage controller for positioning a scanning point

摘要

A scanning device includes a transducer which scans the tracks of a record carrier by a scanning point of radiation. The transducer is mounted movably on a slide which can be displaced in a direction transverse to the tracks by means of a slide drive motor. At least a portion of the transducer is movable relative to the slide, by energizing an actuator. A tracking Control circuit keeps the scanning point on a track by adjusting the actuator control signal (Va) as a function of a tracking error signal. A slide speed control circuit controls the speed of the slide according to a predetermined speed profile provided by a slide speed reference signal (Vrefs). A scanning point speed control circuit controls the speed with which the scanning point is displaced transverse to the tracks so it is maintained substantially equal to the slide speed. The device may be used in a tracking mode and in a displacing mode. In the displacing mode the tracking control circuit is active. In the tracking mode the slide speed control circuit as well as the scanning point speed control circuit are active.