Patent ID: 6115075
Filing Date: 2000-09-05
Classification: G09G,H03L

Abstract:
A method of adjusting a phase of a dot clock signal for a video signal, said method comprising the steps of:(a) sampling said video signal by a plurality of dot clock signals that are expected to have different phase relationships to said video signal, thereby obtaining plural sets of image data;(b) carrying out a prescribed operation for each set of image data to obtain a phase-related index representing the phase relationship of said each set of image data, and determining a desirable phase for said dot clock signal based on said phase-related indexes of said plural sets of image data; and(c) applying an optimum delay to said dot clock signal to have the desirable phase;wherein said step (a) includes the step of applying a plurality of different delays to a reference clock to generate said plurality of dot clock signals, and sampling said video signal by each dot clock signal to obtain said plural sets of image data respectively representing images at an identical position on a screen;said step (b) includes the steps of (1) calculating values of a function representing sharpness of said plural sets of image data as said phase-related indexes corresponding to said plurality of delays, (2) determining an extreme of said values of said function against said plurality of delays, and (3) selecting a delay among said plurality of delays as the optimum delay to attain the desirable phase, said selected delay corresponding to the extreme of said values of said function; andsaid function is an unequivocal and monotone function with respect to a sum of squared differences between image data values at adjoining pixel positions.