Method and system of achieving accurate white point setting of a

Details Method and system of achieving accurate white point setting of a Method and system of achieving accurate white point setting of a

1993-03-24

1996-04-30

Powell, Mark R.

Television

Image signal processing circuitry specific to television

Color balance or temperature

348173, H04N 931

Patent

active

055129617

ABSTRACT:
A system and method achieve and maintain an accurate white point setting of a CRT display in a computing system. The CRT is initially calibrated by individually driving the individual color cathodes and by measuring tristimulus values and cathode beam current for each of the three primary colors. The tristimulus values are normalized by dividing each value by the beam current producing it, and the normalized values are then stored in a calibration memory contained in the display unit. A table of gamma values representing beam current as a function of video drive voltage is measured and also added to the calibration memory. Calibration of the display is implemented by driving the display controller with a white point value and calculating the cathode beam currents from the stored tristimulus values, required to produce an accurate CRT representation of the signal sent to the display controller. The beam current is sampled through a digital feedback loop, and adjustments are made to the color drive circuitry of the display controller to produce the required beam currents for a given white point. Alternative images can be also used instead of white point images for making periodic recalibrations, by derating the beam currents for a given image according to values stored in the gamma table.

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