Video signal compensation apparatus

Claim 1

A display apparatus comprising a dot matrix type display apparatus for displaying a video signal on a pixel by pixel basis by a dot clock and horizontal and vertical synchronous signals, and a video signal compensation apparatus for compensating the video signal, wherein said video signal compensation apparatus comprises: a dot counter for counting the dot clock and outputting a first count signal indicative of a horizontal screen position; a line counter for counting said the horizontal synchronous signal and outputting a second count signal indicative of a vertical screen position; a screen split control means for producing an output signal according to said first and second count signals which is indicative of a screen split region, said split screen region being one of a plurality of screen split regions; and a correction processing means for correcting an input video signal according to said output signal from said screen split control means and for outputting a corrected video signal to said dot matrix type display apparatus; and wherein said correction processing means comprises: an analog-to-digital converter for converting the input video signal to a digital signal; a look-up-table memory means including therein a plurality of tables each of which has stored therein correction data for a corresponding one of said plurality of screen split regions, said look-up-table memory means being responsive to said output signal from said screen split control means for selecting one of said plurality of tables corresponding to a screen split region indicated by said signal outputted from said screen split control means and for correcting said digital signal from said analog-to-digital converter according to the correction data stored in the selected one of said plurality of tables; and a digital-to-analog converter for converting a corrected digital signal outputted from said look-up-table memory means to an analog signal, said analog signal from said digital-to-analog converter being outputted as said corrected video signal from said correction processing means; wherein the correction data stored in each look-up-table is data prepared by measuring a video signal level versus screen brightness characteristic curve of the dot matrix display apparatus for each of three primary colors in a corresponding one of the plurality of screen split regions and computing an inverse conversion curve to said characteristic curve; and wherein said screen split control means comprises a horizontal split bit selection circuit connected to said dot counter for selecting from bits of said first count signal a bit which is renewed by every horizontal split position and bits which are higher order than said bit, and a vertical split bit selection circuit connected to said line counter for selecting from bits of said second count signal a bit which is renewed by every vertical split position and bits which are higher order bits than said bit, the selected bits of said first and second cut signals being outputted as said signal indicative of a screen split region.