Method and apparatus for adjusting dot clock signal

DETAILED DESCRIPTION An object of the present invention is thus to provide a technique for appropriately adjusting a dot clock for video signals by a simple process.
The present invention is directed to a method of adjusting a phase of a dot clock signal for a video signal.
The method comprises the steps of: (a) sampling the video signal by a plurality of dot clock signals that are expected to have different phase relationships to the 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 the each set of image data, and determining a desirable phase for the dot clock signal based on the phase-related indexes of the plural sets of image data; and (c) applying an optimum delay to the dot clock signal to have the desirable phase.
Since the phase-related index indicates whether the phase relationship between the dot clock signal and the video signal is appropriate or not, a desirable phase can be determined on the basis of the phase-related index.
The delay of the dot clock can be adjusted so that the dot clock has the desirable phase accordingly.
According to one embodiment of the present invention, the step (a) comprises the step of: applying a plurality of different delays to a reference clock to generate the plurality of dot clock signals, and sampling the video signal by each dot clock signal to obtain the plural sets of image data respectively representing images at an identical position on a screen; and wherein the step (b) comprises the steps of: (1) calculating values of a function representing sharpness of the plural sets of image data as the phase-related indexes corresponding to the plurality of delays; (2) determining an extreme of the values of the function against the plurality of delays; and (3) selecting a delay among the plurality of delays as the optimum delay to attain the desirable phase, the selected delay corresponding to the extreme of the values of the function