Abstract: A deflection arrangement is described which comprises several piezocrystal elements which are separately driven by a positive or a negative voltage. In this configuration, there is no elastic hysteresis. The arrangement is particularly suitable for automatic focusing systems.

Abstract: Apparatus for producing a shadowgraph image of a transparent part to be examined, such as part of a video disc. The apparatus includes a source of coherent light, and an objective lens system for focusing the coherent light to produce a divergent beam, a concave mirror disposed in the path of the divergent beam, a transparent plate for supporting the disc to be examined in the aperture of the concave mirror, and a projection screen to receive light reflected from the concave mirror. The apparatus may also include plane mirrors to permit the projection screen to be positioned in a convenient location with respect to the disc being examined.

Abstract: A hot sprue valve assembly is provided for controlling flow of molten material through a hot sprue bushing of an injection molding machine. The valve assembly is particularly designed for use with an injection molding machine for molding centrally apertured record discs, such as video information discs. The valve assembly includes a poppet valve movable between an open position to allow flow of molten disc-forming material into a mold cavity, and a closed position to prevent flow of the disc-forming material into the mold cavity. The poppet valve is designed to mold a central aperture in the disc upon movement to the closed position, and the valve assembly is designed to accommodate air ejector apparatus for removing a solidified record disc from the machine.

Abstract: A video disc player assembly is described employing a fixed base member with a pair of fixed rails, and a movable carriage member employing a pair of linear bearing assemblies in engagement with said rails. A capstan and pulley assembly provides a means for moving the carriage member over the rails in the base member.

Abstract: A spindle assembly is provided for rotatably supporting and driving a video information disc in a video recorder-playback machine. The spindle assembly comprises a vertically extending journal having a generally truncated conical shape and supported for rotation in an inverted position within a complementary shaped spindle housing. Pressurized air is supplied through a plurality of slotted flow paths to the support interface between the journal and the spindle housing for supporting the journal for relatively high speed rotation on a cushion of air.

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: A video disc player is described for use with a video disc having frequency modulated video information recorded thereon in the form of a plurality of concentric circles or a single spiral. The information track comprises successively positioned light reflective and light non-reflective regions. A focused light beam is caused to be positioned over the center of an information track and the light reflected from the information track is gathered by an objective lens for application to electronic circuitry for recovering the recorded frequency modulated video signals. Radial tracking means are described for maintaining the focused light spot to impinge upon the center of an information track. Lens focusing means are described for positioning the objective lens at the optimum focused position above the information track for gathering the maximum amount of reflected light from the information track.

Abstract: A servo control system for maintaining an information detection device, such as a light beam, centered on a moving information track, such as a spiral recording track on a video disc. The system of the invention includes an optical system, a piezoelectric dither element coated with a resistive material, a dither oscillator, circuitry for deriving an intermediate signal indicative of the effect of dither on the detected signal derived from the information track, phase comparison circuitry for deriving a known error signal from a comparison of the dither signal applied to the piezoelectric element and the actual dither modulation of the light beam retrieved from the information track.

Abstract: A recording medium, such as a light-reflective video disc, having a plurality of substantially parallel information tracks, each track formed by a succession of spaced, information-bearing indicia having reduced reflectivity. Each track records both a modulated carrier signal and a pilot signal, the pilot signal having a prescribed frequency substantially lower than a substantial portion of the modulated carrier signal. The duty cycle of the spaced indicia forming each track varies in accordance with the phase angle of the recorded pilot signal, and the pilot signal's phase angle is aligned with itself on adjacent tracks.

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 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 data handling system is described for encoding an input digital data waveform by a pulse code modulation technique useful to obtain optimum packing density for a recording medium. The encoding technique selects the binary one state of the input waveform for processing and generates an encoded waveform containing sufficient signal level transition to reconstruct the original input data waveform. The decoding technique examines the transitions present in the retrieved encoded signal and generates decoding indicia sufficient to identify all binary ones in the original digital waveform. A waveform generator recreates the original encoded waveform using selected clocking signals and the decoding indicia.

Abstract: A reproducing objective lens for videodiscs comprising five single lenses for which the working distance is large and flatness of field and resolving power are high.

Abstract: A video signal play back device derives video signals from successive tracks formed as a continuous spiral on a video disc using a light source and a lens system, which is carried by a rotatable element at a predetermined spacing from the surface of the disc and which defines a folded optical path. The rotatable element translates the lens system in the radial direction relative to the disc for "coarse" steering of the light beam along the information tracks as the disc is rotated by a turntable. The optical path includes a mirror which is articulated for rotational motion about an axis which shifts the point of impingement of the transmitted light beam upon the disc in the radial direction. The returned beam is directed to a photosensitive pick-up which provides input signals to a circuit which generates a "fine" servo control signal to drive the articulated mirror.

Abstract: A cover for a video record has a generally unbroken rectangular perimeter. A record player has permanent magnets that cooperate with paramagnetic inserts in the record cover to open the cover for loading and unloading a recording disk. The player has a clamp mechanism that enters the opened cover to clamp the disk for these operations.

Abstract: A servo control apparatus for maintaining a scanning device, such as a beam of radiation, aligned with an information recording track on a moving recording medium, such as a record disc. The apparatus is especially adapted for use in correcting for tracking deviations brought about by temperature-induced expansion and contraction of the disc, which causes the recording track being scanned to move radially outwardly or inwardly relative to the beam of radiation. In the preferred embodiment, the apparatus includes a movable mirror for oscillating the beam in a radial direction, in accordance with a periodic dither signal. This causes a corresponding variation in the intensity of the beam reflected by the disc, with the amplitude and phase angle of this intensity variation, relative to that of the dither signal, indicating the direction and magnitude of the deviation of the beam from the track centerline.

Abstract: In a video disk system a mark along a record data track is modulated in length to represent multi-bit binary code blocks of a first length (such as three or fout bits) and the player system associated with the disk operates in multi-bit code blocks that are generally longer (for example eight bits) so that two marks on the disk may represent a single code block in the associated system. The bits of the code block in the associated system are assigned to bit positions of the appropriate number of marks on the disk in a way that minimizes the effect of errors in the operation of initially writing or subsequently reading a mark. The increments of mark length are also made non-linear to further minimize the effect in the associated system of errors in mark length.

Abstract: An apparatus for performing a Hadamard transform on video data for compression of data to be recorded and decompression of data read from a record for display achieves the necessary high rate by means of two or more adders and two subtractors operating in parallel. A store that holds the data during successive passes through an arithmetic unit has accessing circuits and a set of registers and associated gates that fetch and store the data in a repetitive sequence that simplifies storage accessing. Data is processed in units that represent for example eight lines of a television picture and an output buffer is provided for the decompressor of a video disk player that receives data as it is processed and holds previously processed data unit by a storage accessing circuit that minimizes the amount of buffer storage that must be provided in the player.