Patent ID: 7298916

Claim:
An image signal processing apparatus comprising: frequency correction means that corrects frequency characteristics of analog image signals; A/D conversion means that converts analog image signals that have undergone frequency correction in the frequency correction means into digital image data; clock generation means that supplies sampling clocks to the A/D conversion means, and also that is structured such that phases of the sampling clocks can be adjusted; level difference calculation means that determines a value of a difference in level between two adjacent dot waveforms in the A/D converted image data; maximum value detection means that determines a maximum value of the level difference value in one screen for each phase of the sampling clocks; comparison means that compares a threshold value obtained by subtracting a predetermined value from a maximum value of the determined level difference value with a level difference value determined by the level difference calculation means, and outputs a comparison result signal when the level difference value is higher than the threshold value; counting means that counts the comparison result signals; and control means that controls the clock generation means, and controls phases of the sampling clocks, and also controls frequency characteristics of the frequency correction means in accordance with a count value of the counting means.