Optical scanning unit for projecting a beam onto an optical record carrier with positional control using sets of three coils with each set connected using two amplifiers

An optical scanning unit for controlling and directing a radiation beam towards recording tracks on a surface to be scanned of an information carrier, which scanning unit comprises an objective, a translational-position and angular-position detection system for detecting the position of the objective and an electro-magnetic actuating means for correcting the position of the objective relative to the information carrier in response to electrical error signals supplied by the translational-position and angular-position detection system, the actuating means comprising a movable objective holder which comprises a cylindrical axially magnetized magnet with magnetic poles at its axial ends and at least three sets of coils disposed in the magnetic field of the magnet, which sets are arranged adjacent one another viewed in the circumferential direction of the magnet and cooperate with the magnet via an airgap, characterized in that each set of coils comprises two peripheral coils which are each situated substantially within the magnetic field near opposite axial ends of said magnet, and at least one central coil arranged between the peripheral coils, and

• each set of coils is electrically connected to a matrix circuit via only two amplifiers, which matrix circuit receives said error signals and supplies control signals to said amplifiers.