Television – Image signal processing circuitry specific to television – Video reprocessing
Reexamination Certificate
1997-01-25
2001-01-09
Lee, Michael (Department: 2714)
Television
Image signal processing circuitry specific to television
Video reprocessing
C348S501000, C348S712000, C348S713000
Reexamination Certificate
active
06172716
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to certain improvements to circuitry for adjusting the video gain, black level, chroma gain and burst phase of a video signal.
While my previous U.S. Pat. No. 4,604,646 disclosed a satisfactory method and apparatus for such adjustments, newer components permit a simpler more cost effective apparatus with more performance.
OBJECT OF THE INVENTION
The object of the present invention is to provide more economic circuitry for adjusting the video gain, black level, chroma gain and burst phase of a video signal, while at the same time improving its performance.
This was accomplished by taking the original block diagram of U.S. Pat. No. 4,604,646 and simplifying each section while adding an adjustment for video black level and adding metering circuitry to meter the black level. Additionally, the ability to accept separate chroma and luminance video signals, known as Y/C, input and provide an Y/C output was added.
SUMMARY OF THE INVENTION
A video input is received by the composite video to Y/C splitter which provides the luminance portion of the video signal to the luminance processing section and to the synchronizing signal (sync) separator, while also providing the chroma component to the chroma processor.
The luminance processor includes a back porch clamp to supply video with a constant back porch voltage to the sync splitter which splits the sync from the main video signal and directs it to a separate signal path for special processing. The syncless video is applied to a potentiometer which serves as a video gain control whose output is applied to a white clipper which ensures that an excessive video signal cannot be outputted. The video is then amplified and summed with the previously split off sync to form a normal video signal.
The split off sync signal is optionally amplified and clipped to output a standard amplitude over a range of input amplitudes. Optionally sync can be taken from the sync separator or an external sync source. The sync signal is then blanked to remove any residual, DC restored and supplied to the sync summer.
An electronic SPST switch selects between the luminance processor output and the output of the composite video to Y/C splitter to provide a user option of UNITY gain or no processing as well as a split screen function.
The switched luminance is then amplified to provide a standard video level to the luminance output connector.
The chroma processor receives its input from the chroma output of the composite video to Y/C splitter and is provided to three parallel paths—burst processing, active picture processing and unity, only one of which is active at any one time. The three outputs of the three paths are summed in a chroma amplifier which provides the output signal to the chroma output connector.
The luminance and chroma signals are summed to provide a composite output to the composite output connector.
A sync separator receives video from luminance output of the composite video to Y/C splitter and provides horizontal and vertical sync as well as a burst pulse. These waveforms are used to generate a clamp pulse, burst gate, and blanking waveforms. User controlled front panel switches modify these waveforms to provide a UNITY mode in which all processing is set to neutral or UNITY, a SPLIT screen function in which one side of the screen is processed and the other side is UNITY and a MONO function which removes any color burst that might be present.
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following detailed description and accompanying drawings.
REFERENCES:
patent: 4604646 (1986-08-01), Karlock
patent: 5339114 (1994-08-01), Lagoni et al.
patent: 5379075 (1995-01-01), Nagasawa et al.
Dellett and Walters
Lee Michael
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