DIGITALLY CONTROLLED VIDEO PROCESSOR WITH ACCURATE GRAY-SCALE

A digitally controlled video processor has been developed to a target specification including static and dynamic hue accuracy defined by a target area in the chromaticity diagram. The paper shows the conversion between hue errors and RGB drive tolerances and relates these to quantisation levels. It is demonstrated that conventional circuit techniques introduce important errors in such a processor and alternative approaches are described. The implementation of a fast beam current limiter is shown and formulae for the transient hue errors arising from variations in the CRT biassing are elaborated.