Patent ID: 6750839
Filing Date: 2004-06-15
Classification: G09G

Abstract:
A grayscale reference generator suitable for use with a liquid-crystal device (LCD) display, comprising:a source driver suitable for switching one of a plurality of drive voltages to a column of LCD pixels in response to a digital code word, the transparency of each of said pixels varying over a predetermined pixel voltage range, each of said pixels receiving said selected drive voltage at its first terminal and alternately switched between first and second voltages at its second terminal, said source driver comprising a plurality of resistors connected in series and having accessible connection points at each end of said series string and at various resistor-resistor junctions along said series string, said series string producing at least some of said drive voltages when said connection points are connected to respective correction voltages, a plurality of digital-to-analog converters (DACs), each of which is arranged to output a respective one of said correction voltages in response to a digital code word, each of said DACs arranged such that its respective correction voltage is variable over at least a portion of said predetermined pixel voltage range, wherein said correction voltages define a respective number of points along a piece-wise linear curve which compensates for the non-linear relationship between the absolute voltage across an LCD pixel and its transparency, and a digital multiplexer which receives first and second sets of digital code words at its inputs and which selectably provides one of said sets of digital code words to respective ones of said DACs in response to a control signal, said first set of digital code words arranged to produce correction voltages which compensate for pixel non-linearities when the voltages across said pixels are of a first polarity and said second set of digital code words arranged to produce correction voltages which compensate for pixel non-linearities when the voltages across said pixels are of a second polarity, said digital multiplexer switching between said first and second sets of digital code words in synchronization with the switching of said pixels' second terminal.