Abstract: The present invention describes non-linear circuitry for reducing intermodulation distortion occurring in signals recovered from a disc record. The non-linear circuit generates complementary signals in a diode modulator for cancelling the undesired distortion components of the recovered signal. A synchronous detector in a servo loop with the non-linear circuit samples the distortion component of the resultant baseband video signal and applies bias to condition the non-linear circuit to further reduce the distortion-components. A reference signal for the detector is derived from the sound components of the recovered signal.

Abstract: A stylus position sensor for a video disc player apparatus. An electrode secured in fixed relation to a movable stylus is disposed between first and second electrodes to form first and second variable capacitors therewith. The capacitance of the variable capacitors change in accordance with the motion of the stylus related electrode between the first and second electrodes. A time varying signal is applied through fixed impedances to the first and second electrodes, the amplitude of the signal being modulated by voltage variable impedances connected between the first and second electrodes and a point of fixed potential. The modulated signals at said first and second electrodes are coupled to the stylus related electrode and the time average of the summed signal is indicative of the position of the stylus related electrode and thereby the stylus with respect to the first and second electrodes.

Abstract: In an apparatus for detecting defects on capacitive video disc records, a pickup stylus spanning a plurality of information tracks is effectively swept over the recorded disc area by rotation of the disc. The stylus, upon encountering a convex surface defect, is lofted from the disc surface with a consequent reduction in stylus-disc capacitance. The change in capacitance is indicative of the stylus ejection distance and thereby releated to the size of the defect. Transducers monitor the radial position of the stylus and the angular position of the disc. Each time a disc defect generates a defect indicative capacitance change, the coordinates of the defect are recorded as well as the magnitude of the capacitance change.

Abstract: A video disc player having an adaptive bumper apparatus which tracks the signal pickup stylus to maintain a fixed spatial relation therebetween. The bumper is fixed to an electromechanical transducer secured to the stylus arm support carriage. Signals correlated to the relative disc-stylus velocity having frequency components of the once around rate of the disc are adapted to energize the transducer to cause the bumper to follow the motion of the stylus in the radial dimension. Disturbing visual effects resulting from disc defects, etc. which tend to kick the signal pickup stylus fore or aft of the current track position are significantly reduced.

Abstract: A video disc player having a signal pickup stylus for engaging a disc record is equipped with a steering device to provide three degrees of motion to the stylus. The stylus is secured to a stylus arm, the second end of which is compliantly mounted to a support structure. A permanent magnet in the shape of a cruciform with a like magnetic pole at each extremity is secured to the second end of the stylus. Magnetic field producing electric coils are arranged proximate each of the extremities of the cruciform and secured to the support structure so that energization of the coils will apply force to the cruciform causing the stylus arm to pivot about its compliant mounting.

Abstract: A cartridge for a video disc stylus having a stylus-position sensor, including an electrode mounted to the cartridge walls. An appendage is provided on the cartridge wall to position the sensor electrode proximate the stylus, the appendage being contoured to accept a preformed sensor electrode. The sensor electrode is formed from sufficiently resilient material to recover from deformation during electrode-appendage engagement and constrain itself to a particular position in the cartridge by compressive forces developed between the electrode and the appendage.

Abstract: The invention describes a method and apparatus for reconditioning a video disc signal pickup stylus electrode to prevent electrode-disc electrical shorts. An AC or DC potential is repetitively applied during a predetermined period between the stylus electrode and the disc to produce electrical breakdown at the electrode-disc interface and vaporize a portion of the electrode material. In the capacitive type video disc system, the capacitance sensing pickup circuitry is repetitively tuned to couple excessive amounts of rf potential to the stylus electrode.

Abstract: In a system for correcting tracking errors in a video disc player, digital information, corresponding to field numbers is encoded on the video signal during one horizontal line of the res ective vertical blanking interval. Tracking errors, such as a locked track condition or a skipped track condition are detected by noting improper sequence of two or more decoded field numbers. A kicker apparatus is provided to move the signal pickup device in a direction so as to reduce the tracking error.

Abstract: A bidirectional pulse generator for driving a video disc stylus deflector. Responsive to a deflection pulse a charge integrator has its input connected to a polarity selectable current source. The integrator generates a ramped potential output signal having an amplitude proportional to the deflection pulse width and a slope related to the current polarity. Upon termination of the deflection pulse a feedback loop is closed around the integrator to rapidly reset the output potential of the integrator to one of two pre-pulse output amplitudes. A direction control selects the current source polarity and controls the pre-pulse output amplitude and thereby the relative polarity of the output pulse.

Abstract: In certain video disc systems it is desirable to have a stylus position sensing apparatus. An electrode secured in fixed relation to a movable stylus is disposed between first and second electrodes to form first and second variable capacitors therewith. The capacitance of the variable capacitors change relative to the motion of the stylus related electrode between the first and second electrodes. Complementary signals are applied to the first and second electrodes, which signals are coupled proportional to the respective variable capacitances to the stylus related electrode. The algebraic sum of the signals coupled to the stylus related electrode is indicative of the position of the stylus.

Abstract: A stylus assembly for use with a high density information record such as a grooved video disc. The stylus arm includes a first transducer for detecting lateral forces applied by the record groove to the pickup stylus, and a second transducer responsive to signal generated by the first transducer to translocate the stylus and thereby reduce said forces. The adaptive elimination of lateral forces to the stylus reduces stylus and disc wear and reduces the probability of record imperfections causing the stylus to radially skip over grooves.

Abstract: Apparatus in a video disc player for previewing or scanning information on a record disc. A position sensor detects the position of a playback stylus relative to the carriage assembly for translating the stylus radially across the disc. The position sensor output signals energize a stylus skipper mechanism to translate the stylus a prescribed number of information tracks in accordance with the stylus carriage bias exceeding a threshold value. The carriage is manually moved across the record with the sensor and skipper mechanism cooperating to translate the stylus in consonance with the carriage movement.

Abstract: An improved error code used for encoding and decoding data in a video disc system of the type wherein the data format comprises a start code followed by an error code and information bits. The error code is chosen so that the error code check register in the video disc player begins with the start code in the register, and, if no errors are detected after the full message is received, also ends with the start code in the register. This unique code simplifies both the control logic and the decoding logic in the video disc player decoder.

Abstract: In a video disc player intermodulation distortion can occur during signal recovery and is manifested as the modulated sound carrier appearing in the baseband video. To reduce such distortion, a portion of the signal recovered from the disc record is filtered to extract the modulated sound carrier. This signal is applied to a phase shifting circuit having a predetermined frequency response to condition the modulated sound carrier to have a phase characteristic substantially similar to the phase response of the modulated sound carrier appearing as distortion in the baseband video. The phase conditioned sound carrier is then amplitude adjusted and linearly subtracted from the baseband video signal.

Abstract: In a video disc recording and playback system, the video fields on the disc are identified by digital information recorded during the vertical blanking interval. The recorded digital information includes in the order named, a Barker start code sequence, an error detection coset code and information bits which include a field number corresponding to the video field being recorded. The arrangement results in improved noise immunity and simpler decoding hardware in the video disc player. The digital information is utilized to control a number of functions during the playing of a video disc record such as the calculation and display of elapsed playing time, lifting the stylus at the end of the program, and the detection and correction of locked groove conditions.

Abstract: A video disc playback system for detecting field number information recorded on a sectored video disc and representing stylus location, and for correlating presently received field number information with previously received field number information. Presently received field number data is correlated to previously received field number data to determine whether or not the presently received data indicates the playback stylus to be playing back from a predicted sector of the disc and within a predicted range of radius from the center of the disc. These range and sector checks are used to reduce the probability of data errors passing undetected during playback.

Abstract: An integrated circuit having circuitry for clamping input terminals that remain unconnected after assembly into a system. A transistor is connected to clamp the input terminal to reference potential and provide regenerative feedback to a NAND circuit forming a latch which maintains the transistor on when the input terminal would otherwise be left floating. Alternatively, when the terminal is connected to supply potential, the transistor is maintained "off", precluding loss of power.

Abstract: A video disc playback system includes a circuit for detecting degradation in signals recovered from a disc and generates a control pulse responsive to the detected degradation. The degradations are of a predetermined duration and represent a predetermined percentage decrease in amplitude. A peak detecting and following circuit is connected for receiving signals recovered from the disc record. The decay rate of the peak detecting circuit is arranged to be substantially equal to a certain minimum duration of amplitude degradations that should occur before it is desired to generate the control pulse. The output signal from the detector circuit is proportioned by a divider circuit and then integrated to produce a signal which is proportional to the average of the detected signal over a relatively long period of time. The proportioned signal is applied to the reference signal terminal of a comparator circuit and the detected signal is applied to the signal input terminal of the comparator.

Abstract: A gated oscillator implemented with cascade-connected inverting logic circuits and resistor-capacitor timing elements generates oscillations so long as an inhibiting signal is not applied to one of the logic circuits. Means are provided to maintain potentials on the timing elements during application of inhibiting signal, which potentials are equivalent to steady-state operating potentials at the inception of a state transition. When the inhibiting signal is discontinued allowing oscillations to be generated, the initial pulse period is equal to the steady-state pulse period.

Abstract: A stylus assembly for damping impulsive radial motion of the stylus during playback of a grooved video disc record. Included in the stylus assembly is a moment arm perpendicularly attached at the free end of the stylus arm and parallel to the disc record when the stylus is engaged for playback. A mass is mounted to the moment arm to contribute increased inertia to lateral motion of the stylus only in a direction radially across the record. The mass is designed to permit tracking a record groove in the presence of groove eccentricity but to resist motion due to impulsive forces imparted by record defects or particulate matter thereon.