Active distortion elimination circuitry for a video disc player
AssigneeRCA Corporation
InventorGeorge H. N. Riddle
Life of this patent
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Abstract
In a video disc system, the picture display is adversely affected by intermodulation distortion occuring in the signals recovered from the disc record. A non-linear circuit, responsive to a bias signal, generates a compensation signal in a diode modulator for cancelling the undesired distortion components of the recovered signal. The resulting distortion after cancellation is measured in a comparator circuit to determine if the distortion has increased or decreased. The comparator circuitry outputs an appropriate signal to bias the non-linear circuit to further reduce the distortion components. A small oscillation is superimposed on this bias signal, which oscillation simplifies the comparator circuitry and forces the circuit to search for an optimum operating point.
Claims16
A disc record player comprising:
- means for recovering modulated information signals including video signals and intermodulation distortion components from a disc record;
- a non-linear compensating means responsive to a bias signal for reducing said intermodulation distortion signal components in the recovered signal;
- signal summing means having an output terminal connected for applying said bias signal to said compensating means, said summing means having a first input terminal connected for receiving a reference signal, and having a second input terminal;
- and
- further means responsive to said intermodulation distortion components for generating a control signal at an output terminal thereof;
- and
- means connecting the output terminal of said further means to the second input terminal of said summing means, wherein said bias signal is related to the composite of the control signal and the reference signal and tends to reduce said intermodulation distortion components.
In a disc record player for information recovery of video signals including synchronizing pulses and sound signals, an apparatus comprising:
- first means for recovering modulated information signals including video signals from a disc record;
- a non-linear compensation means, coupled to said recovery means and responsive to an applied bias signal for reducing intermodulation distortion components in the recovered signals;
- second means coupled to said compensation means, for demodulating the information signals, said demodulated signals containing said intermodulation-distortion components;
- third means coupled to said second means for generating a further signal related to the amplitude of the intermodulation distortion components in the demodulated signal;
- fourth means coupled to said third means for modulating said further signal with a constant amplitude oscillating signal to provide a modulated bias signal;
- and
- fifth means coupled to said fourth means for applying the modulated bias signal to the non-linear compensation means.
Dependencies are inferred from the claim text.