The electron gun for a large screen color picture tube generally employs quadrupole lens, so that the landing spot with positive astigmatism can cancel the negative astigmatism from the deflection magnetic field in certain sense.

• 大屏幕彩色显像管电子枪通常采用非轴对称四极透镜 ,其目的是形成一定正像散的着屏光点以抵消偏转磁场产生的负像散。