JPS6466691A - Unevenness of brightness correction system - Google Patents

Abstract

PURPOSE: To realize a high quality picture and also to reduce cost by adding the output of a cathode-ray control means to the output of a corrected waveform generating circuit, which forms a waveform for correcting uneven luminance through the parabolic waveform of a cathode-ray tube(CRT), and thereby improving uniformity of picture luminance of a CRT display. CONSTITUTION: With an observation that the distribution of measurements of uneven luminance of CRT closely resembles a quadratic curve, an offsetting parabolic (quadratic) waveform is used for the correction of luminance. The parabolic waveform required for the formation of correcting signals can be easily taken out from the horizontal or vertical deflection circuit of CRT 1. In other words, the output of a cathode-ray control means 3 for fluctuating the picture luminance of CRT 1 is added, by an adding means 4, to the output from a correcting waveform generating circuit 2 by the horizontally and vertically periodical parabolic waveforms of CRT 1. As the cathode-ray control means 3, any one of the following may be selectible, first grid, cathode or second grid.