| 摘要 |
PURPOSE:To enable secured astigmatism correction to be carried out easily by adjusting the astigmatism-correction image area appearing on the screen of a Braun tube so that it changes from the center of the screen to every direction, and stopping the supply of a first and a second amplitude-modulation wave into a first-and a second-direction astigmatism-correction member. CONSTITUTION:The astigmatism-correction image area appearing on a screen 5a is periodically changed so that it gradually expands from the center of the screen 5 to every direction, symmetrically, before it returns back instantaneously, to the center by controlling the finger recessions of a first and a second potentiometer 17 and 18. After such an adjustment is carried out, a first and a second amplitude-modulation wave (SM1) and (SM2) are stopped from being supplied into a first-and a second-direction astigmatism-correction coil by turning off a first and a second switch 25 and 26. |
