Abstract: The device comprises on the one hand an elongate scale (7) consisting of a succession of magnetic north poles and south poles, and on the other hand a measuring head (9) with at least a first and a second magnetic field sensor (21, 23) which are subjected to the effect of a magnetic field which alternates as a function of time due to the alternating passage of north poles and south poles during a displacement (15) of the scale in its longitudinal direction with respect to the measuring head. The two magnetic field sensors (21, 23) are arranged so that they are always situated opposite one and the same point on the scale (7), the first sensor (21) being sensitive to variations in the magnetic field component extending parallel to the longitudinal direction of the scale (7), the second sensor (23) being sensitive to variations in the component extending parallel to the connecting line (19) between the scale (7) and the measuring head (9).

Abstract: Disc player includes a housing with a frame (11) carrying a scanning device and a disc-drive means for driving discs of different types. Loading mechanism includes a drawer (51) which is movable along guide means between an extended position and a retracted position to move a disc towards and away from the disc-drive means where a movable disc-pressure member (99) presses the disc against the disc-drive means. The disc-drive means comprises a first turntable which is fixedly supported relative to the frame and a second turntable (19) which is movable relative to the frame and can be positioned on the first turntable. A movable holder (21) can be actuated by the loading mechanism to position the second turntable on and remove it from the first turntable.

Abstract: A disc player comprising two drivable turntables (14, 19) on a common supporting member (4) which can be swung about a swing axis between a first position in which a disc supported by one turntable will be in a play position opposite to a clamping member (21) and a second position in which a disc supported by the other turntable will be in the play position opposite to the recording member. The two turntables are coupled for their drive to the same motor (11) supported by the supporting member, the supporting member being swingable through 180 between the first position and the second position.

Abstract: The invention relates to an apparatus for playing back and/or recording information on rotary optical discs comprising a device for clamping the optical disc in position on a disc aligner mounted on a rotating spindle. The clamping device comprises a disc loader which moves with clearance in a support which is movable between a rest position and an operating position. The disc loader exerts a clamping force on the disc during operation due to a magnetic force between magnets secured to the disc loader and the support. Rattling and an oblique position of the disc loader are precluded in that the magnets are arranged to exert a magnetic force which acts between the support and the disc loader so as to clamp the disc loader against the support when the latter is not in its operating position.

Abstract: An optical disc player has a carriage (10) which can be moved to project outside the housing (1) and carries a drive motor (2) having a spindle (4) with means (6) for supporting a disc (40). The player also includes an optical reading device (7) having an optical read head (8) which is movable over the surface of the disc. The reading device (8) is secured in the housing (1) and the housing comprises aligning means (11) which align the spatial position of the rotational axis (3) of the drive motor (2) accurately relative to the optical reading device (7).

Abstract: In an optical device an objective is moved axially along its optical axis relative to a frame in a parallel guide by means of first electro-magnetic actuating means connected to the objective and second electromagnetic actuating means arranged on the frame, which first and second actuating means co-operate axially with each other by means of a magnetic field which is oriented transversely of the optical axis and transversely of the direction of movement of the objective. In order to suppress vibrations caused by axial reactive forces transmitted from the second actuating means to the frame, axially resilient damping means are arranged between the frame and at least a part of the second actuating means. The movements of the second actuating means do not affect the position of the objective because an axial displacement of the radial magnetic field does not give rise to an axial movement of the objective.

Abstract: By means of a radiation beam, an apparatus writes or reads information on an information surface of a rotary optical information disc (21), which apparatus comprises an objective frame (16) on which an objective (17) for concentrating the radiation beam to a radiation spot is mounted by means of a parallel guide (19) in such a way that it can move in the direction of its optical axis (18). The objective is protected against dust, contaminants and mechanical damage by means of stationary plane-parallel radiation-transparent shielding means (22), which are interposed between the objective and the rotary information disc, the lens system of the objective being corrected for the optical properties of the shielding means.

Abstract: An optical focussing device for focussing a radiation beam emanating from a radiation source onto a record carrier (1), and more specifically for focussing a light beam onto a video disc or audio disc, comprises a frame (3) in which an objective (10) is movable axially in the direction of its optical axis (15) with the aid of a drive system (4-7, 16). In order to avoid damaging of the record carrier (1) at last one elastic bumper (37) is secured to the free end (11) of the objective (10), which bumper absorbs shocks and prevents marring of the record carrier in the event of contact between the objective and the record carrier.

Abstract: An arrangement for centering, aligning and retaining a rigid disc such as a rapidly rotating video disc in an operating position, comprising a centering device mounted on a drive spindle, which device cooperates with a central disc hole in the disc, comprising a disc aligner mounted on the drive spindle for aligning the disc in a plane perpendicular to the axis of rotation of the drive spindle in the operating position of said disc, and comprising a disc loader for loading the disc towards the disc aligner. The disc aligner is rigidly connected to the drive spindle and the centering device comprises a plurality of resilient centering members which cooperate with the wall of the disc hole and which are radially movable between a rest position and an operating position which is situated nearer the axis of rotation of the drive spindle.

Abstract: The position of an optical or opto-electronic component, such as a lens or a plate provided with a number of light-sensitive semiconductor diodes, can be adjusted in two directions of adjustment which are perpendicular to each other with the aid of an appropriate adjusting device. The adjusting device comprises two bending hinges consisting of portions of a leaf spring, which bending hinges are perpendicular to each other, the one hinge being bent relative to a stationary frame to which the adjusting device is secured and the other bending spring being bent relative to the first bending spring. The two bending springs may consist of portions of a single unit manufactured from a suitable spring material.

Abstract: An optical disc player comprises a read objective on a carriage which is translated to and fro with the aid of a drive unit with an electric motor by cooperation of a drive pinion and a gear rack, so that the read objective travels between a minimum diameter and a maximum diameter of the disc to be read, between which the information is contained. A pinion and a gear wheel of the drive unit cooperate with each other without play, in that the pinion is mounted on a pivoting member which is resiliently loaded, so that the pinion and the gear wheel are in resilient engagement with each other. During work on the optical disc player the pivoting member can be pivoted away by hand, so that the teeth of the pinion and the gear wheel are disengaged from each other so that a quick, practically unhampered translational movement of the carriage is possible.

Abstract: The spindle motor of a video disc player is simultaneously disengaged from the motor power source and connected to an electromagnetic safety device for maintaining the cover of the player in a safety position by virtue of the induction current generated by the freely spinning motor until the motor speed is reduced to a safe angular velocity. An electromagnetically operated brake powered by the inductive current generated by the motor assists in reducing the motor velocity.

Abstract: A video disc player comprises a cam body which is mounted on a cover, which cam body has a cam for latching the cover in a closed playing position and for actuating a main motor switch. The cam body carries an additional latching cam with the aid of which the cover is already latched when the cover is not yet fully closed, the playing position is not yet reached, and the main motor switch is not yet actuated.

Abstract: A video disc player provided with a housing and a latched hinged cover. By unlatching the cover the main motor power is switched off, a brake brings the drive spindle to a standstill, the radiation beam power is switched off, and a guard blocks the radiation beam path.

Abstract: An optical focussing device for focussing a radiation beam on a record carrier, more particularly for focussing a light beam on a video record, the objective being included in an electronic position control system with the aid of an electromagnetic drive system by which it can be moved parallel to its optical axis. The parallel guide for the objective consists of a cylindrical bearing bush which is connected to the frame of the device, in which bush the lens mount of the objective is an accurate axially slidable fit. The lens mount preferably has an outer surface of opalized aluminium and the bearing bush an inner surface which contains PTFE.

Abstract: A clamping device for rotatably driving an information carrying record such as a rigid or flexible video record and comprising a drive spindle, a record support disposed thereon, a substantially conical centring member having a diameter which varies from a diameter smaller than to greater than that of the record hole, which also during operation co-operates with the edge of the central hole in the record, and furthermore resilient pressure means for pressing the centring surface and the edge of the central hole in the record against each other.

Abstract: A playback apparatus, in particular a video player, for playing back round disks, which are provided with information tracks which are optically readable with the aid of a read beam obtained from a light source, and having a housing which comprises a substantially flat covering plate and an optical focussing device movable to and fro in a slot in the covering plate. In view of the safety of the apparatus and for other, such as aesthetical, reasons the slot is closed by a closing element in every position of the focussing device, which element is connected to the focussing device and for example consists of a flexible strip of a width greater than the width of the slot.