Electro-optical scanning device having bridge members through tracking coils

Claim 1

An electro-optical device for scanning an information track on an information carrier, comprising a frame plate, a holder which is movable relative to the frame plate and in which an objective having an optical axis is mounted, which holder can be translated parallel to the optical axis and can be rotated about an axis of rotation which extends parallel to the optical axis, bearing means for supporting the holder relative to the frame plate, magnetic means which are arranged on the frame plate and which surround the axis of rotation and at least two cylindrical wall portions which are connected to the frame plate and which surround said magnetic means in such a way that an annular air gap is formed between said wall portions and the magnetic means, the magnetic means and the cylindrical wall portions forming part of a magnetic circuit with a radial magnetic field in said air gap, a focussing coil which is secured to the holder, which is movable in the air gap, and which is arranged coaxially around the axis of rotation, and at least two tracking coils which are secured to the holder and which extend through recesses between said cylindrical wall portions and are situated externally of the focussing coil, the tracking coils having turns situated in radial planes containing the axis of rotation of the holder, the turns of each tracking coil surrounding a continuous space, and the focussing coil and the tracking coils, when energized, both cooperating with the magnetic circuit for controllably moving the objective, characterized in that bridge members of a soft-magnetic material extend through respective said continuous spaces to magnetically link the cylindrical wall portions at both sides of each of the tracking coils.