Abstract: A disc-shaped record carrier is described on which information is recorded in an optical structure of trackwise arranged areas and intermediate areas. By adapting the average dimensions of the areas to the average spatial frequencies on the record carrier a read signal can be obtained of sufficient modulation depth and minimal distortion. This is accomplished by increasing the track width with decreasing radius of the record carrier.

Abstract: An opto-electronic coupler uses a light emitter and a photo-sensitive receiver, which are each associated with transparent bodies of revolution having convex and cylindrical portions.

Abstract: A method of imaging a three-dimensional object with the aid of coding and decoding using coherent point codes, whereby the object is recorded in two steps, each with a plurality of radiation sources of different orientation on the same recording material.Negatives of the two images are produced, after which the positive of one image is combined with the negative of the other image, the combined images being subsequently multiplied by means of point holograms formed with the aid of a reference wave and a multiplicity of light sources whose co-ordinates correspond to those of the point images of the two source arrays recorded by a pinhole camera, the two multiplied images being superposed in one plane, the coded images being decoded by changing their scale with the aid of two synchronously controlled zoom lenses whereby the coordinates of the point image function of an image of an object layer in the coded images are adapted to the points stored in the two point holograms.

Abstract: A head-worn viewing device for alleviating night blindness includes an image intensifier tube between periscopic reflectors with an objective lens in front of the upper reflector and an eyepiece lens behind the lower reflector. The objective and upper reflector are mounted for rotation together about a pivot so that, for short viewing distances, a continuous adjustment is provided which will refocuss the objective at the front plane of the intensifier tube and compensate for the parallax of the periscopic reflectors.

Abstract: Time division multiplex telecommunication exchange in which each bit group received is compared, in the incoming line circuits, with the preceding bit group. When two successive bit groups are equal, the second group is not supplied to the switching device which serves for the exchange of data between the connected transmission lines. The outgoing line circuits retransmit the bit group when no new bit group is received from the switching device within a predetermined time.

Abstract: A servo system for controlling the position of a magnetic reading head relative to the center of a selected information track. During writing, long-wave track sensing signals are written below the data signal in parts of the tracks and that in such manner that corresponding parts of successive tracks alternately contain or do not contain track sensing signals. During reading, the head reads not only the information of the selected track but as a result of crosstalk also reads the track sensing signals of the adjacent tracks. After filtering and processing the track sensing signals a control signal for controlling the head is obtained. Application in particular in helical and transversal scan video recorders.

Abstract: Apparatus for reading a record carrier on which a television signal is recorded. In order to ensure an accurate time error measurement for a time error correction device, use is made of a burst signal which is locked to the horizontal synchronizing pulses. Said burst signal may be constituted by the color burst signal or an additional burst signal which is superimposed on the horizontal synchronization pulse. In order to obtain a pilot signal for the time error measurement a keying signal is generated with the aid of a generator which is controlled by the horizontal synchronizing pulses, the beginning of said keying signal being situated within the time interval of the burst signal. The first zero passage of the burst signal which appears after the beginning of said keying signal is employed as a pilot signal for the time error measurement.

Abstract: Apparatus for optically reading and/or recording information on a rotary record with the aid of a radiation beam, in particular a video player, in which a carriage which is movable to and fro underneath a deck and carries a focussing device with an objective, as well as a number of other optical elements belonging to a scanning device and, as the case may be, a radiation source for producing the radiation beam. In order to prevent dust and other air-borne contaminations from settling on the optical faces of the optical elements of the scanning unit, at least a number and preferably all optical elements are protected against dust by a dust cover.

Abstract: In a circuit arrangement for a dropout detector for the detection of dropouts in signals which are reproduced from a record carrier, the signal path includes an amplitude discriminator before the threshold device which supplies a switching signal in the event of a dropout, the discriminator characteristic between two threshold levels of the output signals having a steep edge for amplitude discrimination in whose range the signal level which is decisive for the actuation of the threshold device is situated.

Abstract: A conductor for the transport of light between a photo-emitter and a photosensitive receiver.Light conductor comprising a conductor element having total reflection the main face of which has substantially the shape of a hemispherical surface part and in which the emitter and the receiver are situated diametrically in the vicinity of the spherical surface part.Application especially to photocouplers having a semiconductor emitter and receiver.

Abstract: An optical storage system for the simultaneous or random storage of digital information in a plurality of channels, comprising a rotating storage disc which is scanned by a light beam. The digital information of each channel is stored in points along a spiral track comprising interruptions. A concentrical guide track is associated with each channel. The light beam being focussed onto both tracks of each channel for optical addressing. The light beams of all channels are controlled via deflection systems so that, during the interruptions, they are briefly directed onto the guide tracks while following the spiral tracks. From the radial deviation of the moving disc, measured by way of a detector system, control signals are derived by the deflection systems to compensate for undesired radial motions of the spiral-shaped tracks.

Abstract: A light-beam deflection system for scanning documents of large format, in which a switchable very narrow light-beam is passed over a series of stationary plane mirrors whose centers are arranged on a parabola and whose inclination with respect to the document onto which the reflected light-beam is directed is that of the tangent to the parabola at the point of contact with corresponding mirror center.

Abstract: Digital transversal filter for realizing a lowpass filter with a cut-off frequency f.sub.g and an impulse response h.sub.1 (i), a lowpass filter having a cut-off frequency 2f.sub.g which has a transfer characteristic which is in phase with the first-mentioned lowpass filter, as well as a lowpass filter with a quadrature transfer characteristic of the in-phase filter.

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: When the information of a continuous-motion video record is displayed in the stop-motion mode by repeated display of two fields which form an interlaced picture, motion in the scene gives rise to a frame-frequency flicker phenomenon in the stop-motion picture. By forming suitable video signal combinations in discrete groups which each comprise two associated fields and by recording these combinations in the video record, the flicker phenomenon in a stop-motion picture is eliminated without continuous display being perceptibly affected.

Abstract: A thin-film magnetic head having improved playback properties in which the gap-bounding core parts overlap each other laterally while enclosing a layer having a gap and in which a first core part has the shape of a closed loop and is bridged in the center by a second core part. The parts of the first core part on either side of the bridge are provided with identical coils, while the first core part at the area of the overlap is divided centrally by an extra gap. Upon playing back, the difference signals of the coils then provides an indication as regards the position relative to the track.

Abstract: A record carrier is described which is provided with an optically readable structure of trackwise arranged areas alternating with intermediate areas. Areas of at least two different types are provided. As a result, a high information density can be achieved. The different types of areas may also be used for centering a read beam relative to a track and for focussing the beam onto the track.

Abstract: A method of recording and reproducing audio information on a disc shaped record carrier. During recording the audio information is divided into consecutive information segments of a duration .tau..sub.t. Each information segment is subjected to time compression before recording. The duration .tau..sub.t and the time compression are selected so that optimum use is made of the recording capacity of the record carrier without information loss. During reproduction the information segments are subjected to a complementary time expansion and recombined in their original sequence.

Abstract: A pivoting mirror device for pivoting a pivoting mirror about two mutually perpendicular pivoting axes under the influence of electric control signals, in particular for a video player which reads information from a video disk with the aid of a light beam using optical means, the mirror being journalled so as to be pivotable to all sides and the device comprising electro-dynamic drive means which include permanent magnets and control coils for controlling the pivoting movements. The mirror is supported near its center, while permanent magnetic positioning means which co-operate with permanent magnetic means which are connected to the mirror continually subject the bearing to pressure.

Abstract: An automatic optical focusing system suitable for an apparatus for reading an information track on a record carrier with the aid of a read spot which is focused in an imaginary focusing plane and which is formed by a radiation beam which is produced by a radiation source, more in particular suitable for a video disc player which employs optical reading, and serving for automatically keeping the read spot focused at the plane in which the information is disposed (information plane) during playing of a record carrier, comprising an optical focusing device, an oscillating optical element which cooperates with the radiation beam and which can effect high-frequency oscillations so that a high frequency oscillation of small amplitude about the coarse position of the focusing plane is obtained, an electromagnetic drive system for the high-frequency drive of the oscillating optical element, a radiation-sensitive detector which responds to the radiation beam which has been modulated by the information track, and a con