Patent ID: 6590620
Filing Date: 2003-07-08
Classification: G09G,H04N

Abstract:
A horizontal distortion correction apparatus for correcting horizontal distortion caused by an assembly error of a CRT display apparatus that displays an image by scanning a video signal, based on a horizontal synchronizing signal included in the video signal; comprising:deflecting means for deflecting an electron beam to display the image on the CRT; a PLL circuit operable to control a display position oft he image by applying a horizontal pulse in synchronization with the horizontal synchronizing signal to said deflecting means; and residual phase adding means for providing a residual phase for said PLL circuit to shift a phase of said horizontal pulse in a direction so as to cancel out the horizontal distortion; said PLL circuit comprising: a phase comparator operable to compare the horizontal pulse with a flyback pulse to produce a phase difference signal indicative of a difference between the horizontal pulse and the flyback pulse indicative of a start of horizontal deflection scanning for each horizontal synchronization period; a low pass filter operable to convert the phase difference signal into a DC phase difference voltage based on a modulation signal; a distortion-correcting wave form generator operable to produce the modulation signal to modulate the DC phase difference voltage; a resistor; a waveform adjuster connected through said resistor to said distortion-correcting wave form generator operable to adjust the wave form of the modulation signal; a voltage controlled oscillator operable to produce an oscillation signal having a frequency corresponding to the phase difference signal based on the DC phase difference voltage; a 1/N frequency divider operable to divide the oscillation signal into a predetermined frequency to produce a frequency-divided signal; a pulse generator operable to produce a pulse having a predetermined duty ratio based on the frequency-divided signal; and a horizontal output device operable to produce a horizontal deflection current and the flyback pulse based on the pulse; wherein the modulated signal is supplied to the PLL circuit to control the phase of the horizontal pulse so that the image scanned in a horizontal direction is displayed without distortion in the horizontal direction.