Raster distortion correction circuit
AssigneeRCA Corporation
InventorsRobert F. Casey, Werner F. Wedam
Life of this patent
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Abstract
In an apparatus for displaying the picture information of an incoming interlaced television signal in noninterlaced raster scanning display on the faceplate of a picture tube, each video line of the television signal is separated into R, G and B color component signals. Each video line is compressed, or speeded-up, at a variable rate and delayed by a variable delay time to provide a speeded-up signal that is coupled to the corresponding electron beam gun of the picture tube. Each of the variable rate and delay is controlled in accordance with information relating to distortions of the raster scanning display. In this way, distortion, such as east-west or convergence, is reduced when the speeded-up signal is displayed.
Claims24
A video display apparatus responsive to an incoming interlaced video signal containing picture information for generating therefrom a noninterlaced video signal that contains in a given video line signal thereof a plurality of pixel signals derived from said interlaced video signal for display in a corresponding plurality of pixel locations of a corresponding display line of said video display apparatus, said video display apparatus being subject to a distortion that, if left uncompensated, results in erroneous pixel locations during noninterlaced display of said pixel signals, said apparatus comprising:
- a memory coupled to said interlaced video signal for storing said picture information of said interlaced video signal in said memory;
- first means coupled to said memory responsive to a varying clock signal for generating said plurality of pixel signals contained in said noninterlaced video signal from the picture information stored in said memory;
- second means for generating a correction signal that varies in accordance with said distortion;
- and
- third means responsive to said correction signal for generating said varying clock signal that varies in accordance with said correction signal wherein said first means generates said plurality of pixel signals in a manner that varies in accordance with said varying clock signal so as to compensate for said erroneous pixel locations.
A display apparatus responsive to an incoming video signal for generating an output video signal coupled to a video display apparatus to provide information that is displayed in a plurality of display lines on said video display that form a raster during a given deflection cycle such that a distortion in said video display apparatus that is associated with the display of picture information derived from said incoming video signal in said raster is compensated by varying said output video signal, comprising:
- a memory responsive to said incoming video signal for storing therein the picture information derived from said incoming video signal and for reading out therefrom the stored picture information to generate said output video signal that provides the stored picture information to said video display apparatus;
- means for generating a correction signal that varies in accordance with said distortion in said video display apparatus;
- a controlled oscillator for generating a first clock signal that is coupled to said memory to generate said output video signal at a rate that is determined in accordance with the frequency of said clock signal, said controlled oscillator being responsive, outside a calibration interval, to said correction signal for varying the frequency of said first clock signal in accordance with said correction signal;
- and
- means for generating a calibration reference signal having a value during said calibration interval that is representative of a first operating frequency, wherein said controlled oscillator is responsive during said calibration interval to said calibration reference signal for providing calibration of the operation of said controlled oscillator during said calibration interval.
Dependencies are inferred from the claim text.