Automatic peaking control circuitry for a video processing system
First Claim
1. Automatic peaking control circuitry for a video processing system having an aperture correction stage for generating pre-shoot and over-shoot signals comprising:
- bias means for providing an adjustable gain control signal to said aperture correction stage;
detecting means connected to said aperture correction stage for detecting the amplitude of said pre-shoot and over-shoot signals in excess of a predetermined threshold; and
gain control means connected to said detecting means and to said bias means for automatically controlling the gain of said aperture correction stage to track said adjustable gain control signal.
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Accused Products
Abstract
A video processing system for a television receiver is shown. The video processing system includes a gain controlled stage through which a video signal is coupled. The gain of the stage is controlled to provide contrast control of the video signal. The video signal is also applied to an aperture correction circuit which develops an aperture correction signal including a pre-shoot transient responses. The aperture correction signal is also coupled through the gain controlled stage so that it is amplified or attenuated by the same amount as the video signal. An automatic peaking control circuit receives the pre-shoot and over-shoot signals to generate an automatic control signal to control the gain of the aperture correction circuit. A tracking control circuit causes the automatic peaking control circuit to accurately track the setting of an adjustable control which controls the gain of the aperture correction circuit. The output of the gain controlled stage is coupled to an output stage where the black level of the video signal is controlled by a black level control circuit. The disclosed video processing system is further adapted for fabrication in integrated circuit form.
13 Citations
12 Claims
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1. Automatic peaking control circuitry for a video processing system having an aperture correction stage for generating pre-shoot and over-shoot signals comprising:
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bias means for providing an adjustable gain control signal to said aperture correction stage; detecting means connected to said aperture correction stage for detecting the amplitude of said pre-shoot and over-shoot signals in excess of a predetermined threshold; and gain control means connected to said detecting means and to said bias means for automatically controlling the gain of said aperture correction stage to track said adjustable gain control signal. - View Dependent Claims (2, 3, 4, 5)
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6. Automatic peaking control circuitry for a video processing system having an aperture correction stage comprising:
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bias means including a manually adjustable impedance connected to said aperture correction stage for controlling the gain thereof; detecting means connected to said aperture correction stage for detecting the amplitude of aperture correction signals in excess of a predetermined threshold; and gain control means connected to said detecting means and to said bias means for providing an automatic gain control signal to said bias means in response to the detected aperture correction signals. - View Dependent Claims (7, 8, 9, 10)
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11. A tracking control circuit for tracking the setting of an adjustable impedance comprising:
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a reference diode and a first resistor connected in series with said adjustable impedance for receiving a current proportional to the setting of said impedance; a first controlled transistor having a base connected to said reference diode and a second resistor connected to an emitter of said first controlled transistor, said first controlled transistor having a collector current proportional to the current through said reference diode and proportional to the ratio of the magnitudes of said first resistor and said second resistor; and a second controlled transistor having a base connected to said reference diode and a third resistor connected to an emitter of said second controlled transistor, said second controlled transistor having a collector current proportional to the current through said reference diode and proportional to the ratio of the magnitudes of said first resistor and said third resistor. - View Dependent Claims (12)
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Specification