Abstract: The invention relates to an electro-optical device, comprising a frame (1), a movable holder (5) in which an objective (7) having an optical axis (9) is secured, bearing pin (25) fixed to the holder (5) and bearings (27, 29) fixed relative to the frame (1) supporting the holder so that it can be translated and rotated, a magnet (13) secured to the frame and cylindrical wall portions (1B) which wall portions with the magnet form an annular air gap (17) with a radial magnetic field. A focussing coil (19) is secured to the holder and is movable in the air gap, and a plurality of tracking coils (33) are secured to the holder and are situated on the outer side of the focussing coil. The tracking coils extend through recesses (37) between the cylindrical wall portions of the frame, the turns of the tracking coils being situated in or substantially in radial planes containing the axis of rotation (11) of the holder and the turns of each of the tracking coils together forming a continuous free space (35).

Abstract: An optical scanning unit with an objective for the focussing a beam of radiation along an optical axis into a scanning spot on the surface of an information carrier. The scanning unit also has an electromagnetic drive for correcting the position of the objective with respect to the information carrier. The drive has an objective mount supported in an annular, moving magnetic member which is axially magnetized and is arranged coaxially about the optical axis. The drive is further provided with fixed coils which interact with the magnetic member via an air gap. The fixed coils are arranged along at least three radial planes which are normal to the optical axis. Two planes lie in the area of the axial ends of the centrally positioned magnetic member and the third central plane which extends between the two outer radial planes.

Abstract: The invention relates to an optical scanning unit for controlling and directing a radiation beam towards recording tracks of a surface to be scanned on an information carrier. The scanning unit comprises an objective, a translational-position and angular-position detection system for detecting the positions of the objective and an electromagnetic actuating means for correcting the position of the objective relative to the information carrier in response to the electrical error signals supplied by said position detection system. The actuating means comprises a movable objective holder with an axially magnetized magnet whose axial ends are provided with magnetic poles and at least three sets of coils situated in the magnetic field of the magnet. The coils are arranged adjacent each other viewed in the circumferential direction of the magnet and cooperate magnetically with the magnet via an air-gap.

Abstract: A pivotal-arm device (15) for a disc scanning unit (13) for recording and/or reading information comprises a deck plate (3A), a pivotal arm (25) carrying the scanning unit, and pivotal-arm bearing means. The pivotal arm bearing means comprise two bearings disposed on opposite sides of the pivotal arm, at least one of the bearings comprising two bearing members (31, 33), a spherical bearing element, which cooperates with these bearing members, and a viscous medium. At least one of the bearing members has a concave bearing surface (33A), between which bearing surface and the bearing element a gap (35) is formed, which gap widens towards the edge of said bearing surface and which contains said viscous medium. A resilient element (39), which is secured to the deck plate, urges the bearings towards one another.

Abstract: The disclosed apparatus for recording and/or reading information in or from a track of a radiation-reflecting record carrier by means of a light beam includes an objective system for focusing the light beam so as to form a light spot on the record carrier in dependence on a control signal (S.sub.f). The control signal is generated by a focusing-error detection system having an astigmatic element and four detectors (D.sub.1 to D.sub.4). The output signals S.sub.1 to S.sub.4 of the four detectors are combined in an electric circuit arranged to produce a control signal satisfying the formula: ##EQU1## This control signal drastically reduces the influence on the focusing of offset of the light spot on the four detectors.

Abstract: In an optical device an objective (11) can be moved relative to the frame (1) along its optical axis (13) in parallel guide means (3, 5) by means of an electromagnetic actuating device. The actuating device comprises first actuating means (21) and second actuating means (23) which are connected to the objective (11) and which cooperate with said first actuating means via an air gap (25). The first actuating means (21) are arranged in a mount (27) which is supported by a leaf-spring-shaped element (29) which is secured to the frame (1).