Abstract: An apparatus is described for reading a record carrier on which information is stored in an optically readable reflecting structure. By projecting two radiation spots one before and one behind the plane of the information structure, it is possible to ascertain whether a read beam is properly focussed on the information structure. An optical wedge-field lens combination extends the range of operation of the focus correction device.

Abstract: A record structure for recording with a radiation beam uses a transparent disc or drum, a coaxial backing disc or drum and two coaxial resilient ring-shaped seals to provide an enclosure between the discs or drums. Radiation-sensitive recording material on the side of the disc or drum within the enclosure is thereby protected from ambient dust particles and other contaminations, while the gaseous or solid by-products of the inter-action between the recording material and the radiation beam in the area around which the beam impinges are substantially contained between the disc surfaces and cannot produce deposits on an objective lens used to focus the radiation beam or poison the user.

Abstract: An aspheric element, placed near a principle plane of an wide-angle, wide-aperture image forming system and having in its aspheric function a term proportional to the third power of the distance from the optic axis improves off-axis revolution.

Abstract: A coder and a decoder having delay elements of the same delay time arranged one after the other in which the signal transmission ratio code of the signal paths from the input of the circuit to the output is chosen in accordance with bessel coefficients so as to prevent disturbing echoes.

Abstract: A tracking mirror device, in particular for a video disc player, in which for following an information track on a video disc with a beam of radiation, use is made of a mirror which oscillates at a high frequency, which causes the beam of radiation, which serves for scanning the information track, to oscillate transversely to the information track at a high frequency and a small amplitude, while the filtered out high-frequency signal, as a function of its amplitude and its phase relationship with the high frequency voltage which is applied to the oscillating mirror, yields a control signal for following the information track. In accordance with the invention, use is made of an oscillating mirror which is driven electromagnetically and which is connected to oscillation compensation elements by means of springs which elements oscillate in phase opposition to the mirror. Thus, an oscillator mirror is obtained which can readily be excited to natural resonance and thus requires little power.

Abstract: A playing apparatus, more specifically a video player for playing round records with a central hole, which are made of a transparent material, which records at one side have a transparent surface and at their other side are provided with information tracks which are optically readable with the aid of a read beam, which tracks are covered by a light-reflecting layer. In order to enable both relatively thick rigid records and relatively thin flexible records to be played on one playing apparatus, the invention provides a transparent adapter disc, which together with a flexible record can be positioned on the playing apparatus and driven in a rotary fashion. In order to prevent dust particles from being trapped between the flexible record and the transparent adapter disc, the adapter disc may be provided with a central recess with a number of air admission apertures at the circumference thereof, so that during operation a thin film of air is formed between the flexible record and the adapter disc.

Abstract: An apparatus for optically reading a record carrier on which information is contained in tangentially extending tracks includes a directing system for making the scanning spot cooperate with the desired track. In order to enable a jump-wise displacement of the scanning spot from a track being followed to an adjacent track, a switching device is provided for supplying a suitable control signal to the directing system. The control signal is automatically adapted to varying track distances, so that a correct jump-wise displacement of the scanning spot is guaranteed.

Abstract: An electro-magnetically controllable beam deflection device for use in an optical system for deflecting a radiation beam obtained from a radiation source, in particular for use in video players. The deflection means may for example comprise a pivoting mirror, or an assembly of a plano-concave and a plano-convex lens which with their concave and convex surfaces face each other, and can perform pivoting movements at a small distance from each other. The deflection means is connected to frame by means of an integrated plastic bearing component. The bearing component has a local portion of small cross-section which under the influence of the control forces exerted on the deflection means, is relatively readily deformable. This portion may for example take the form of an integral hinge or of a thin cylindrical portion.

Abstract: A mother for manufacturing long-playing video records is provided by (1) selectively exposing a photoresist disposed as the outer layer on a substrate comprising a disc-shaped plate, a thin layer of base material, e.g., an oxide of nitride, adhering to the plate and a thin metal layer, e.g., chromium, silver, nickel or titanium, coating the base material layer, (2) removing non-activated sections of the photoresist layer and (3) sputter or chemically etching the thin metal and base material layers in sections corresponding to the removed sections of the photoresist layer.

Abstract: An apparatus as described for reading a record carrier on which information, for example video and/or audio information is stored in an optically readible track-shaped information structure. A deviation between the center of a read spot which is projected on the information structure and the center line of a track to be read can be detected with the aid of at least two detectors which are disposed in the far field of the information structure in different quadrants. With the aid of the same detectors a reference signal is obtained which is used for deriving a control signal for correcting the position of the read spot relative to the track to be read.

Abstract: An apparatus for reading a disc-shaped record carrier, which apparatus comprises provisions such as a command device, for reproducing the recorded information in a scanning sequence which differs from that during recording. In order to maintain the line-sequential phase alternation of the color signal during reproduction via a PAL or SECAM receiver, a correction circuit has been provided. The correction circuit comprises a delay line for delaying the chrominance signal by one line period and a recombination circuit with a switch which is controlled by the command device. The recombination circuit, depending on the position of the switch, supplies an output signal which consists of the combination of the luminance signal and either the chrominance signal or the chrominance signal which has been delayed by one line period.

Abstract: A servo system for controlling the position of a magnetic reading head relative to the center of a selected information track. During recording a long-wave positioning signal is recorded below the data signal in the tracks. Upon reading out, the head not only reads the information of the selected track but, as result of cross-talk, also the positioning signals of the adjacent tracks. After filtering out and processing the positioning signals, a control signal for controlling the head is obtained.

Abstract: An apparatus is described for reading a record carrier, on which information, for example video and/or audio information, is stored in an optically readable track-shaped information structure. Errors in the focussing of a read beam relative to the plane of the information structure can be detected with the aid of two detectors which are disposed in the far field of the information structure, which detectors are arranged at one side of a plane defined by the optical axis of an objective system and a line which effectively extends transversely to the track direction and which longitudinal direction are effectively transverse to the track direction. With the aid of the same detectors a reference signal is obtained, which is employed for deriving a control signal for focussing correction of the read beam.

Abstract: A carrier is provided with a spiral structure in which sound and/or image information is stored in the form of frequency modulated or phase modulated signals. The carrier structure is composed of coplanar regions of variable length separated by coplanar areas of variable length. Where the regions and areas are all in the same plane the regions and areas have different coefficients of reflection or transmission. Where the regions and areas are not coplanar they are spaced by a distance sufficient to produce in response to impinging radiation a one-half wave length difference in the radiation exiting the regions and areas.Apparatus for imaging the radiation exiting the carrier structure is also disclosed.This is a continuation of application Ser. No. 396,399, filed Sept. 12, 1973, now abandoned, which is a continuation of Ser. No. 229,285, filed Feb. 25, 1972, now abandoned.

Abstract: A receiver in an adaptive pulse code modulation transmission system is provided with a pulse pattern analyzer which is responsive to at least two sequential information pulses, and a correction circuit controlled by the pulse pattern analyzer for correcting the last transmitted pulse group.

Abstract: The invention relates to transmission systems with dynamic compansion for the coded transmission of speech signals. By the use of a limiting device in the dynamic control circuit of the receiver the intelligibility is improved. The limiting device is such that the dynamic range of a transmitted signal is limited so that no relevant information is lost in the period the human ear needs to adapt itself to rapid sound variations.

Abstract: A pulse code modulation transmission device comprising a transmitter and a receiver each being provided with a dynamic control circuit and a modulator built up of a first controlled current source circuit supplying a supply current for a difference amplifier which is controlled by output pulses from the transmitter and incorporating in its two output circuits pnp current mirror circuits whose outputs are connected to the output of a modulator directly and through a precision polarity reversing circuit, respectively. The control input of the first current source circuit is coupled to the output of the dynamic control circuit as well as to the input of a fourth current source circuit arranged in parallel therewith whose output is connected in the manner of a feedback through a pnp-current mirror circuit to a npn-current mirror circuit whose output is coupled to the output of the dynamic control circuit.

Abstract: A method and apparatus for writing video information with a laser on a recording surface employing a protective foil on the writing surface through which foil the laser write beam is focussed. A stream of filtered gas is passed between the foil and the writing surface to remove any gaseous or particulate by-products of the writing process, and to protect the writing surface from room contaminance.

Abstract: An apparatus for reading a record carrier on which information is stored in an optically readable structure of trackwise arranged areas and intermediate areas where at least one of the surfaces of the record carrier body has periodic surface undulations along the track direction. A focussing error signal is derived by reflecting a focussed light beam on the record surface and by measuring the amplitude and phase of the portion of the reflected beam that corresponds to the surface undulations.

Abstract: An apparatus for reading a disc-shaped record carrier on which information is stored in a preferably spiral-shaped track. Said information is read optically with the aid of a radiation beam, which via a directing system transfers the information contained in the scanning point of the record carrier to a read detector. The radial position of the scanning point is controlled with the aid of a control system which via a first pattern of radiation spots which is projected onto the record carrier receives information about said radial position and by means thereof controls the directing system. In order to ensure that the system is stable under all conditions use is made of a second pattern of radiation spots which are projected onto the record carrier, which pattern is radially shifted relative to the first pattern, and from which a control signal is derived with which the transfer function of the control system is varied so as to stabilize the control system.