Abstract: In a tracking servo system of a recording-disc information reading and reproducing apparatus such as a video disc player, a tracking error signal indicative of an amount of deviation of an information pickup medium such as a focused spot of a scanning beam of light from a target track of the recording disc being scanned is amplified with a gain which is varied as the pickup medium is displaced radially of the recording disc between an outer peripheral area and a central area of the disc.

Abstract: Reflected light from the record in a optical disk player is directed at a string of photo sensitive diodes. Two adjacent diodes of this string of diodes receive light from a selected portion of the track on the disk. The outputs of these two adjacent diodes are summed together to generate the output signal for the optical disk player. The outputs of the two diodes are also subtracted from one another to generate a differential signal for tracking purposes. The magnitude of this differential signal is a measure of the relative magnitudes of the signals on the two adjacent diodes and therefore is one indication of how much of the light from the selected portion of the track reaches each of the diodes. When this differential output becomes larger than a preselected value, decode circuitry responds by changing the combination of adjacent diodes in the string to generate the video output signal and the difference signals.

Abstract: An apparatus is described for reading a record carrier on which information is stored in an optically readable information structure, which apparatus includes a radiation source which supplies a read beam of great coherence length. By including a radiation attenuating element in the radiation path of the read beam, preferably nearest to the radiation source, random intensity modulations in the read beam, which modulations may be caused by undesired reflections in the radiation path, can be substantially reduced.

Abstract: An information signal recording medium of rotary type has a flat surface with successions of pits formed therein as respective concavities in response to an information signal. The successions of pits constitute respective circular tracks of a specific pitch. Each it is formed with a width, equal to the width of a track, which is substantially equal to or greater than said pitch of the track.

Abstract: A record carrier is disclosed having an optically readable information structure comprising trackwise arranged information areas, as well as an apparatus for reading said record carrier. By using two mutually perpendicularly polarized beams components for reading and by giving the information areas of adjacent track portions a different geometries such that areas of one geometry can be read in an optimum manner by only one of the beam components and is virtually not observed by the other beam component, the track distance can be reduced without increasing the crosstalk, so that the information content of the record carrier is increased.

Abstract: The video or television signals are broken into numerous elements representing spaced portions of the video display screen along the line sweep, and imprints (electrical or optical) for each element are made in a path on a rotating medium which may be a disc, drum or belt. The lineal length of each imprint on the path is determined by the light characteristic of the video signal being recorded. Clock marks are permanently recorded in a separate path on the rotating medium, one for each spacing of the line elements, to accurately locate the elements on the rotating medium and thereby accurately locating the elements on the screen when the information is decoded. For the U.S. television operational mode, one rotation of the rotating medium takes place in 1/30 of a second to give a complete picture frame, including interlacing.

Abstract: A reversible optical recording medium is comprised of an electrically conductive layer overlain by a thermoplastic layer containing a light absorptive compound selected from the group consisting of metal complexes of substituted ethylene dithiols having the structure ##STR1## where M is Pt, Pd, or Ni and R and R' are independently alkyl, phenyl or substituted phenyl groups. Information is recorded by sequentially charging the recording medium and then heating it above its softening temperature by absorption of the recording light beam in the thermoplastic layer.

Abstract: An information signal recording system records an information signal, a first and a second reference signals for tracking control, and a third reference signal for switching the first and second reference signals at the time of reproduction on a recording disc. The first and second reference signals are alternately recorded at positions intermediate between centerlines of adjacent information signal tracks. The third reference signal is recorded at a predetermined position on every information signal track. A reproducing system reproduces the information signal together with the third reference, and the first and second reference signals by a single reproducing element. A tracking control signal is produced from the first and second reference signals switched by the third reference signal separated from the reproduced information signal.

Abstract: A symmetrical video disc structure and method for making the structure are described. The video disc structure is symmetrical about a plane passing through a core member and equidistant and parallel to a first information bearing surface and a second information bearing surface carried by the core. First and second reflective layers are formed over the first and second information bearing surfaces, respectively. The combination of two reflective layers, so oriented, operates as a vapor barrier for preventing the absorptions of water into the core member of the symmetrical video disc structure situated between the two vapor barriers. First and second protective layers are formed over the first and second reflective layers, respectively. The thickness of the first and the second protective layers is maintained the same over the entire area of the video disc structure.

Abstract: A record carrier is described in which information is recorded in an optically readable information structure comprising trackwise arranged information areas; as well as an apparatus for reading said record carrier. By arranging the adjacent information track portions on different slopes the track spacing can be reduced without increasing crosstalk.

Abstract: An optical head comprising a semiconductor laser array which is used as a light source, and an optical system which guides laser beams from the array to a predetermined recording medium. The beam from one lasing point of the array is modulated by predetermined information and is used as a recording beam, while the beam from another lasing point is continuously oscillated and is used as a playback beam.

Abstract: A holographic video disc system is described in which the baseband information for successive horizontal television line intervals is recorded as successive holograms of one-dimensional line images in a spiral track on the surface of a disc of material. A spiral guiding track is also formed in the surface of the disc immediately adjacent to the spiral track of holograms. The recording system includes a laser beam which is modulated with the baseband video information. The beam is divided into a reference beam and a data beam. A beam deflector scans the data beam through a chosen angle at the horizontal television sweep rate, while the reference beam is unaffected. The reference beam and data beam are intersected at the surface of a record medium and form a surface relief hologram on that surface.

Abstract: The invention relates to devices for optically recording information on a rotating carrier with a recording spot along a track. In accordance with the present invention, there is provided a reading spot kept at a constant distance, equal to an integral multiple of the pitch of the track, from said recording spot. The reading spot is made to follow an already recorded track element by means of a feedback loop. The simultaneous displacement of the two spots is controlled by a signal obtained by the detection of the reading beam.

Abstract: The disclosure is directed to a system for storing and reproducing analog or digital information, such as television information. There is provided a recording disk having a mechanical guiding track formed in a spiral or circular pattern on a surface thereof.A signal recovery device is provided and includes mechanical tracking means to effect guiding along the mechanical guiding track of the disk. The signal recovery subsystem also includes an optical scanning means for scanning the optical records.In the preferred embodiment of the invention, the signal recovery device includes mechanical driving means, synchronized with the optical scanning means, for engaging the guiding track and causing motion of the disk with respect to the signal recovery device. The disk is preferably mounted on a passive turntable, and rotation of the disk and turntable is achieved by the mechanical driving means of the signal recovery device acting directly on the disk.

Abstract: 6. In combination in a system for reproducing .Iadd.video .Iaddend.information from a rotatable medium where the medium has characteristics at progressive positions along a spiral path for modifying energy directed at the medium in representation of .Iadd.video .Iaddend.information previously recorded on the medium where the information recorded on the medium at each successive position along the spiral path represents substantially less than a complete visual image,means operatively coupled to the medium for producing a continuous rotation of the medium,pickup means disposed relative to the medium including,means for directing .[.energy.]. .Iadd.a beam of energy having a radius not greater than approximately one micron to enable the reproduction of the video information .Iaddend.