Color and brightness tracking in a cathode ray tube display system

Color and brightness tracking control apparatus for a color cathode ray tube display instrument system subjected to viewing under a wide range of ambient light conditions comprising

• (a) a cathode ray tube having a display screen for emitting images in a plurality of different colors dependent upon the individual and variable energization of cathode means for producing at least three individual primary colors the relative brightnesses of which determine said plurality of colors,
• (b) video command means for commanding a predetermined plurality of colors in which a plurality of images are to be displayed, each of said colors comprising a plurality of predetermined components of said primary colors at predetermined relative brightness levels,
• (c) ambient light sensor means for providing a signal which varies in accordance with the extremes of ambient light intensities existing in the vicinity of said display instrument,
• (d) digital computer means including
• (i) memory means containing data representing the individual cathode energization required to produce each of said primary color component relative brightness levels required to produce each of said predetermined plurality of colors over said range of ambient light intensity conditions, and
• (ii) processor means responsive at least in part to said light sensor means for continuously computing a reference display brightness dependent upon the existing ambient light intensity conditions and for deriving from said memory means the cathode energization data required to produce each of said predetermined plurality of colors at the existing ambient light intensity conditions, and
• (e) means responsive to said video command means and said derived cathode energization data for energizing said cathode means to thereby produce said predetermined plurality of color images at the existing ambient light intensity conditions.

A method of operating a color cathode ray tube (CRT) display instrument, which is viewable under a wide range of ambient light conditions, with the aid of a digital computer, comprising

• (a) providing said computer with a stored data base peculiar to said CRT display including at least a plurality of cathode drive excitations required to produce a corresponding plurality of brightnesses of each of the CRT's primary color emissions,
• (b) constantly measuring the ambient light conditions in the vicinity of said display,
• (c) constantly providing the computer with said ambient light measure,
• (d) repetitively calculating in the computer at a rate substantially greater than the refresh rate of said CRT display, a reference display brightness compatible with said ambient light conditions, and
• (e) repetitively extracting from said data base at said calculation rate a cathode drive excitation corresponding to the brightness of each color component emission for the existing ambient light conditions.