G - Physics – 09 – G
Patent
G - Physics
09
G
375/46, 355/6
G09G 1/28 (2006.01) H04N 9/16 (2006.01) H04N 9/69 (2006.01)
Patent
CA 1216688
ABSTRACT OF THE DISCLOSURE An apparatus for color and brightness correction for a multi-gun color CRT display, providing compensation for variation in phosphor efficiency with cathode energization and for color tracking between guns. The brightness correction circuit is required to respond only to essentially DC changes, while a color selection circuit responds at a video rate. In a preferred digital embodiment, brightness and color tracking correction factors are stored in memory dedicated to a particular CRT, and addressed in response to input from a reference brightness level selected by an operator. A color selection decoder having stored in a second memory relative brightness characteristics of each color phosphor as a function of the hue commanded converts an input binary command to an analog output, which is combined with the brightness and color tracking correction factor to determine the resulting cathode energization for each color gun. In an analog embodiment, brightness and tracking corrections are performed by a logarithmic amplifier which applies an appropriate multiplier factor to the reference brightness level. Color selection is provided by a variable gain amplifier having gain control bias varied by a digital color decoder in proportion to the desired relative brightness levels. A hybrid system is also described combining digital memory storage for brightness and tracking correction and an analog variable gain amplifier for relative brightness compensation, using the circuits described above.
429702
Smart & Biggar
Sperry Corporation
LandOfFree
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