Television – Image signal processing circuitry specific to television – Gray scale transformation
Reexamination Certificate
2005-03-22
2005-03-22
Lee, Michael H. (Department: 2614)
Television
Image signal processing circuitry specific to television
Gray scale transformation
C348S687000, C348S379000
Reexamination Certificate
active
06870576
ABSTRACT:
An automatic beam limiter circuit (ABL circuit) calculating an average of a video signal at least a portion of the video signal is provided. After a converter circuit converts an analog signal, which is generated from the video signal, to a digital signal, a horizontal and a vertical average circuits calculate a horizontal and vertical averages of the digital signal at least a portion of the digital signal. The portion of the digital signal is a scanned line of the digital signal on a CRT. A comparison circuit compares a first calculation value calculated between a reference value and the vertical average with a second calculation value calculated between the reference value and the horizontal average, and outputs a first comparison signal and a second comparison signal based on the comparison results. A gain control circuit produces a gain control signal for adjusting the brightness/contrast in response to the first comparison and second comparison signals. Advantageously, the automatic beam limiter circuit is capable of efficiently preventing a frame delay in controlling the brightness/contrast of the video signal and the rapid increase of beam current when a black field is rapidly changed into a white field.
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F. Chau & Associates LLC
Lee Michael H.
Tran Trang U.
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