| 摘要 |
PROBLEM TO BE SOLVED: To make the width of displayed characters constant at all times independently of the position on a screen by controlling a frequency from a voltage controlled oscillator to be gradually lower from both ends of the screen in the horizontal direction toward the center in the mode converting the width of the screen of an existing aspect ratio nonlinearly to a prescribed value. SOLUTION: A character signal is superimposed on a video signal equivalent to one scanning line on a screen during interlace scanning, a sine wave oscillator 7 is used to apply waveform conversion based on a horizontal synchronizing signal inserted to both ends of the video signal and a full rectifier circuit 8 generates a correction signal. The correction signal is oscillated as a control input of a voltage controlled oscillator to obtain a reference correction signal inversely proportional to an input voltage whose oscillating frequency is lower in the middle of the screen at horizontal deflection and whose oscillated frequency is higher toward both ends of the screen. The reference correction signal is used to drive a character signal generating circuit to obtain the character signal compressed laterally nonlinearly. |
