Abstract: An apparatus is described for reading, by means of a beam of radiation, a disk-shaped information carrier which contains spirally arranged video and/or audio signals coded in optical form, which apparatus comprises a source of radiation and a radiation-sensitive signal detector cell, the information carrier being disposed in the radiation path between this source and this detector. By providing at least one grating, consisting of radiation-transmitting and radiation-absorbing stripes and on which an image of part of the grating-shaped structure of the information track in the vicinity of the portion of this track to be read may be formed, and a radiation-sensitive detection system, an accurate indication of axial and radial displacements of the optical imaging system relative to the information carrier can be obtained.

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 automatic optical focussing system, suitable for a video disc player, comprising an optical focussing device with an objective which is moved to and fro at high frequency in the direction of its optical axis by electro-dynamic drive means, the superimposed high frequency component of the signal which has been modulated by the information tracks on the video disc being employed for automatic control of the position of the objective. In view of a low power consumption the objective is connected to an oscillation-compensation element by means of at least one resilient element, for example a circular plate, which compensation element is axially movable or relative thereto, and which together with the objective and the resilient element constitutes a mechanical resonant system. On the resonant system a piezo-electric acceleration transducer may be mounted with the aid of which the mechanical resonant system can be included in a self-oscillating loop.

Abstract: A device for compensating dropouts in color television signal modulated by a carrier wave. The modulated video signal is applied to a first delay line, from whose output signal a luminance component delayed by one line period is derived with the aid of a demodulator, and is also applied through a second demodulator and a chrome separating filter to a second one line delay line. The sum of the delayed chrominance and luminance components are substitution for the demodulated color television signal during a dropout.

Abstract: A circuit arrangement for phase-alignment of a servo drive for a rotary system, to whose correction element for correcting the speed of said system the output signal of a phase detector is applied via a transmission path which output signal determines the mutual phase relationship of an actual signal and of the desired signal, comprises two gate circuits of which one circuit receives the pulse-shaped actual signal and the other circuit receives the pulse-shaped desired signal as an input signal, and whose output signals are applied to the transmission path in phase opposition for phase-alignment of the rotary system, each of the gate circuits being controlled by a bistable multivibrator which can also be changed over by said actual and desired signals, so that a gate circuit is opened only when its input signal contains more than one pulse between two consecutive pulses in the input signal of the other gate circuit.

Abstract: The invention relates to single lenses with large aperture and large field.The paraxial parameters of a lens with spherical refractive surfaces are selected in advance. The lens aberrations are corrected in such a way by aspherization of the refractive surfaces, that the wave front aberration which is expanded in a series as a function of the aperture, at least contains sixth-degree terms.The invention may be employed in heads for reading audio or video information on rotary record carriers.

Abstract: A method of decoding composite images of three-dimensional objects which are coded by means of a large number of radiation souces of different perspective and which are decoded by means of a point hologram. The point hologram is produced by means of a flat reference beam and by illuminating a shadow mask in the converging beam. The coordinates of the shadow mask correspond to the point image of the source distribution recorded by a hole camera, while the coordinate differences of the holes of the shadow mask have the same value, or a value increased to scale, with respect to the coordinate differences of the point image function of the object plane of the composite image which was nearest to the source distribution during the recording. The decoding of the composite image is effected by shifting between an illumination lens and the point hologram in an incoherent monochromatic converging beam.

Abstract: A monochromator provided with a plurality of entrance windows for beams of white light emitted by respective lamps which are alternately operated. The internal optics of the monochromator consist of a dispersing system disposed so that each of the beams of white light is intercepted and converted into dispersed light which is composed of discrete monochromatic light beams of different wavelengths. The monochromator has an exit window with a slit of predetermined dimensions so as to transmit only one wavelength at a time.

Abstract: A system comprising a playback unit and an associated long-playing record on which sound information is recorded in a time division multiplex code on several tracks. Upon reproduction the same track is scanned n times with the aid of a beam of light before this beam of light is directed to the next track. With the aid of a sampling gate the pulses comprising the sound information in time division multiplex code and associated with a first sound channel are sampled with the aid of said sampling gate while during a second revolution pulses from a second sound channel etc. are sampled.In order to operate this sampling gate in synchronism with the scanning of said pulses the playback unit comprises first synchronizing means responding to pulses also comprising the sound information. Furthermore, at the commencement of each track, starting pulses are provided to which second synchronizing means respond.

Abstract: An electrodynamically controllable pivoting mirror device for an apparatus for optically reading an information carrier with the aid of a beam of radiation, in particular for a video-disc player which utilizes optical reading, the mirror device being provided with a frame on which a mirror, which is mounted with the aid of an elastic plastic, is pivotably disposed, which mirror is pivotable by means of electrodynamic control means consisting of electromagnets and/or control coils.

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: Parallel data transmission system in which the data signals are converted to multilevel digital signals and transmitted through the channels of a frequency division multiplex system. To compensate for the delays between the data signals received in the various channels of the multiplex, a pilot signal is transmitted in each channel in the form of a signal which only has a real component. At the receiver side a filter circuit is used which comprises a first fixed coefficient part at whose input the data signal is multiplied by a component of the received pilot signal and a second part having two variable coefficients which are derived from the two components of the received pilot signal.

Abstract: A telecommunication system in which two terminal stations are coupled to one another via a telephone exchange and the transmission paths between the exchange and the terminal stations are provided with pairs of modems for transmitting, via the transmission paths, information signals of modulation types which are different in the terminal stations and in the transmission paths, the modems nearer to the exchange being switched off by means of an auxiliary signal the frequency of which corresponds to a component of the frequency spectrum of the modulation type employed in the transmission path. Thus information transmission in the telephone exchange is obtained in the same modulation type as employed in the transmission paths so that unnecessary conversion from one type of modulation to the other is avoided.

Abstract: A recording device for storing and playing back information in which mechanical deformations which are representative of the stored information are provided in the surface of a record carrier consisting of a permanent magnetizable material or being covered with such a material. As a playback element is present a sheet of monoaxial magnetizable material which comprises a single-walled magnetic domain ("bubble"). The size of the domain is modulated upon moving the recording medium with respect to the sheet. Deposition of the domain in the sheet upon playing back can be corrected by way of fine control.

Abstract: An apparatus is described for reading a radiation-reflecting record carrier on which information is stored in an optically readable track-shaped phase structure. The apparatus inter alia includes a radiation source, an objective system and a radiation-sensitive detection system. By a suitable arrangement and a suitable choice of the power of a cylindrical lens, which lens in conjunction with a four-quadrant detector supplies a focussing signal, it is possible to detect centering-errors with the aid of only two additional detectors in the plane of the four-quadrant detector.

Abstract: An electromagnetically controllable pivoting device for pivoting a reflecting surface of a pivoting mirror about pivotal axes parallel to said surface with the aid of electrical control signals, more particularly intended for a video disc player in which a light beam is produced by means of a light source, which beam is aimed at an information track of a rotating optically readable video disc by means of the reflecting surface of the pivoting mirror. The mirror is supported by a bellows body of an elastically deformable plastic, which bellows body is provided with at least one rotation-symmetrical fold which is concentric with the optical center of the reflecting surface.

Abstract: An apparatus for reading a record carrier in which information, for example video and/or audio information, is recorded in at least one track is described. By means of a detection system which comprises two radiation-sensitive detection elements which, viewed in the direction of length of the track, are arranged one behind the other so that they intercept two different parts of a radiation beam which has been modulated by the information of the track, positional errors of the plane of the track relative to a signal detection system can be detected.

Abstract: A non-linear pulse code modulator wherein input signals are coded into digital representations of amplitude range segments and amplitude in excess of the minimum amplitude within the respective range segment uses a first analog-to-digital converter having a sawtooth-shaped control characteristic to determine the amplitude range segment from an input signal sample. The output of the first analog-to-digital converter is used to effectively divide the signal sample by a factor 2.sup.n, where n corresponds to the determined range. The result of the division is then converted in a second analog-to-digital conversion to a digital signal that is combined with the digital range segment signal for transmission thereof.

Abstract: An apparatus is described for reading a flat record carrier on which information is stored in an optically readable track-shaped information structure. By the arrangement in the far field of the information structure and at one side of a plane which is formed by the optical axis of an objective system which is used for reading and a line parallel to the center line of the track portion to be read, of a radiation-sensitive detection system which consists of at least two detectors in approximately the position .beta./2, .beta. being the angle at which a first-order beam is diffracted in the lateral direction of the tracks, centering and focussing errors can be detected without the use of auxiliary beams and additional optical elements.

Abstract: The invention relates to a recording and/or playback apparatus for video signals, equipped with a rotary head system with at least one recording and/or playback head and at least one erase head for the trackwise erasing of a video signal recorded in the video tracks, which tracks cross a further track, specifically a synchronization track, the erase signal being applied to the rotating erase head via a time-controlled gate circuit, which interrupts the path of the erase signal to the erase head while said head scans the further track, thus preventing a signal recorded in the further track from being erased.