Abstract: A method and apparatus for encoding a plurality of bytes of digital data into a further plurality of bits suitable for storage in a storage medium, and for recovery therefrom, and for decoding the stored bits retrieved from the storage medium, for the recovery of the encoded bytes. The digital data bytes are arranged into a plurality of code blocks, each having a first predetermined number of columns and a second predetermined number of rows of bytes. A parity block of bytes of data is generated having a number of columns and a number of rows of bytes corresponding to the first predetermined number of columns and to the second predetermined number of rows of bytes, respectively, of the code blocks, the bits of data in the parity block corresponding to the computed parity of the combined corresponding bits in each of the code blocks.

Abstract: A video recorder-playback machine is provided for recording and/or playing back video information from an information disc. The machine includes a "write" laser and a "read" laser respectively for generating record and playback optical beams which are focused upon the disc by an optical record-playback head. An optics carriage movably positions the head with respect to the disc in moving optical alignment with the "write" laser and carries the "read" laser in fixed optical alignment with the head. The machine includes apparatus for monitoring the record optical beam during operation in a record mode, and for substantially simultaneous operation in a playback mode to monitor the playback optical beam during the recording process.

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 method for recording video and audio information onto a recording medium which involves recording a carrier frequency signal, frequency modulated with composite color video information, and a subcarrier frequency signal, modulated with audio frequency information onto the recording medium and selecting the frequencies of the carrier and subcarrier signals such that the subcarrier frequency is lower than the second lower chroma sideband of the modulated carrier signal.

Abstract: Apparatus for verifying the accuracy of insertion of code signals in the vertical intervals of video signals. The code signals are inserted in accordance with a procedure characteristic of a specified encoding format. The accuracy of insertion is verified by testing the codes against a predetermined set of conditions related to the procedure. Failure to meet one of the conditions results in the generation of an error signal.

Abstract: Apparatus for generating a map of detectable characteristics of a disc. A scanning signal display device has a detector coupled to the intensity input thereof. The detector detects the characteristics at a location on the disc which is scanned in a spiral pattern and provides a signal representative of the detected characteristics to the display device. A signal is generated and provided to the drive inputs of the display device to cause the trace of the device to follow a spiral pattern corresponding to the scan pattern of the predetermined location.

Abstract: A video recorder-playback machine is provided for recording and/or playing back video information from an information disc. The machine includes a "write" laser and a "read" laser respectively for generating record and playback optical beams which are focused upon the disc by an optical record-playback head. An optics carriage movably positions the head with respect to the disc in moving optical alignment with the "write" laser and carries the "read" laser in fixed optical alignment with the head. The machine includes apparatus for monitoring the record optical beam during operation in a record mode, and for substantially simultaneous operation in a playback mode to monitor the playback optical beam during the recording process.

Abstract: A drop-out detector for detecting the absence of a pulse in either of first and second pulse trains, especially for use with the spindle servo error generator of a videodisc mastering machine. Prior attempts at providing a drop-out detector function for the spindle servo error generator rely on the use of RC based timing circuits to create time windows within which to look for the presence or absence of a reference or tach pulse, as the case may be. Such arrangements provide satisfactory performance in connection with constant angular velocity type discs, since reference and tach frequencies remain constant throughout the mastering process. However, problems arise in utilizing such RC based circuits in connection with constant linear velocity type discs. The present invention overcomes these problems by operating on a pulse width modulation technique for controlling the spindle motor speed.

Abstract: An improved method and apparatus for recording and playing back a video signal on a video disc, such that selected video frames can be played back in a stop-motion fashion, with accompanying audio. Each stop-motion video frame is recorded on a single recording track on the disc, and an associated digitized stop-motion audio signal is combined with a continuous-play video signal and recorded on a plurality of preceding tracks. During playback, the tracks recording the continuous-play video signal are first scanned, to recover and display the continuous-play video frames, and to recover and enter into a memory the digitized stop-motion audio signal. The track recording the corresponding stop-motion video signal is then scanned, in a repeated fashion, to provide a stop-motion display of the video frame, while the stop-motion audio signal is extracted from the memory and converted back to its original analog format, for playback along with the stop-motion video frame.

Abstract: A method for measuring the size of dimple-type defects in an area of the surface of a flat piece of transparent material, such as an optical disc. A large beam of collimated light is provided and passed through the piece of material in a normal orientation with respect to the surface being inspected. A screen is placed in the path of the beam emerging from the disc and circular shadows generated by refraction are measured to determine the size of the defects which produces them.

Abstract: Apparatus and process for writing information using a laser light writing beam focused on a light sensitive layer having a threshold power level above which the layer reacts to the laser write beam. The intensity of the writing beam is adjusted relative to the threshold power level. In one embodiment, the peak intensity of the writing beam is adjusted so that one-half of the peak intensity is equal to the threshold power level. In a second embodiment, the average intensity of the writing beam is adjusted to equal the threshold power level.

Abstract: Method and means for evaluating the quality of audio and/or video transfer characteristics of a device upon which, or through which, audio and/or video information is contained, or passes, respectively. Both method and apparatus concern the evaluation of the quality of information transfer in the recording and playing back of a recording medium or in the transferring of audio and/or video information through an information handling device referred to as a throughput device. Unit evaluation is accomplished by establishing an input signal of known content, measuring selected parameters of selected parts of the input signal, feeding the input signal to the unit under test, measuring the parameters of parts of the output signal from the unit under test corresponding to the same selected parts of the input signal, and comparing the selected parameters of the input signal with the corresponding parameters of the output signal.

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: An improved method and apparatus for recording and playing back a video signal on a video disc, such that selected video frames can be played back in a stop-motion fashion, with accompanying audio. Each stop-motion video frame is recorded on a single recording track on the disc, and an associated digitized stop-motion audio signal is combined with a continuous-play video signal and recorded on a plurality of preceding tracks. During playback, the tracks recording the continuous-play video signal are first scanned, to recover and display the continuous-play video frames, and to recover and enter into a memory the digitized stop-motion audio signal. The track recording the corresponding stop-motion video signal is then scanned, in a repeated fashion, to provide a stop-motion display of the video frame, while the stop-motion audio signal is extracted from the memory and converted back to its original analog format, for playback along with the stop-motion video frame.

Abstract: A servo control system for maintaining an information detection device, such as a light beam, at the optimum focused position above an information track for retrieving the maximum amount of reflected radiation from an information track, such as a spiral recording track on a videodisc. The system of the invention includes an optical system, a piezoelectric dither element, a dither oscillator, circuitry for deriving an intermediate signal indicative of the effect of the dither on the detected signal derived from the information track, phase comparison circuitry for deriving an error signal from a comparison of the dither signal applied to the piezoelectric dither element and the actual dither modulation of the light beam retrieved from the information track, and a movable lens assembly responsive to the error signal for accurately focusing the light beam upon an information track.

Abstract: A method for detecting and measuring eccentricity in a video disc and a video disc player, in which a video signal representing a special eccentricity test pattern is recorded on a prescribed set of adjacent recording tracks on the disc. Each frame of the video signal is recorded on a separate track, and the successive frames exhibit a prescribed movement. During an eccentricity test, the player scans the disc at a fixed radius, so that eccentricity in either the disc or the player causes it to scan cyclically across a plurality of tracks during each disc revolution. The playback signal therefore includes segments of the signal recorded on each of the scanned tracks, the shape of the displayed test pattern indicates the magnitude of combined eccentricity of the disc and player.

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 hot sprue assembly is provided for controlling flow of molten material into the mold cavity of an injection molding machine. The hot sprue assembly is particularly designed for use with an injection molding machine for molding centrally apertured record discs, such as video information discs. The hot sprue assembly includes a hot sprue bushing cooperating with a generally conically-shaped dispersion head to define an open and relatively narrow annular gate through which molten material is injected into the mold cavity, and a central die plug within the mold cavity for cooperating with the dispersion head to mold a central aperture into the disc. Valving of the molten material through the gate is achieved by heating the sprue assembly to create a temperature differential which, during solidification of the material within the mold cavity, permits the material within the mold cavity to solidify up to the gate without substantial solidification of material within the sprue assembly.

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: Method and apparatus for generating a series of delta modulation data signals corresponding to a predetermined analog waveform wherein an error determination comparison is made on a sequentially generated series of potential delta modulation data signals to determine the optimum pattern of delta modulation bits. The method can be performed in iterative fashion for each delta modulation bit generated.