White uniformity correcting apparatus for a three-color display wherein correction signals are stored in a memory

Claim 1

A dynamic white uniformity correcting apparatus for a three-color display, said display being for displaying a color picture in response to three primary color signals and comprising a cathode-ray tube, said cathode-ray tube comprising means for emitting a plurality of electron beams and a display screen divided into a plurality of incremental areas, said display further comprising deflection means for scanning said plurality of electron beams across said display screen to produce said color picture in response to said three primary color signals, said apparatus comprising: a correction signal generating means for generating at least two correction signals for each incremental area of said display screen, said correction signal generating means comprising a correction signal storage means for storing said correction signals; at least two amplitude modulators, each of said amplitude modulators being for adjusting the level of a different one of said three primary color signals in response to a corresponding one of said correction signals; and means for reading out said correction signals from said correction signal storage means as said plurality of electron beams are scanned across corresponding incremental areas of said display screen, and for supplying said read-out correction signals to said amplitude modulators to adjust the levels of the corresponding primary color signals, thereby correcting the white uniformity of said color picture displayed on said display screen, wherein said correction signal storage means comprises a plurality of pattern memories, each of said pattern memories corresponding to a different orientation of said display screen relative to the earth's magnetic field, and wherein said reading out means reads out said correction signals from the pattern memory corresponding to the particular orientation of said display screen relative to the earth's magnetic field.