| 摘要 |
PROBLEM TO BE SOLVED: To correct the shortage of horizontal size at the vertically central part of a display screen by performing modulation control to time intervals for reading stored display data out of a frame memory, and equalizing picture element intervals over the entire surface of a tube. SOLUTION: Distortion is generated since the center of curvature on the fluorescent surface of a CRT 20 is different from the center of deflection. Concerning horizontal linearity correction, modulation control is performed to time intervals for reading the stored display data while using speed correction data in a reading speed correction memory 7, and read data are inputted from a frame memory 4 to a video circuit 14 after D/A conversion. Thus, the output display picture element intervals are made uniform. Since the modulation control is performed so as to shorten the reading time intervals by correcting just by an amt. of an elongated component concerning elongated distortion but to prolong the reading time intervals by correcting just by an amt. of a contracted component concerning contracted distortion, the intervals of picture elements displayed on the tube can be made uniform. |
