普通电视机的电子束聚焦电路均采用可调整的直流高压加到聚焦极。电视机出厂前,将聚焦一次调好,可保持基本上不变。但是,无论显像管是弧形面还是平面,电子枪到荧光屏之间的距离都不可能相等,否则,屏幕表面将成为该距离为半径的弧度极大的曲面。实际上,显像管或投影管中,即使是老式非平面屏幕,其等效半径也远大于电子枪到幕面的距离。因此,在电子束扫描 The normal television electron beam focusing circuit are adjustable DC high voltage is applied to the focusing pole. TV set before leaving the factory, the focus will be adjusted at a time, can remain basically unchanged. However, regardless of whether the tube is arcuate or flat, the distance between the electron gun and the phosphor screen can not be equal, otherwise the screen surface will become a very large curved surface with a radius of curvature. In fact, the tube or projection tube, even the old non-flat screen, the equivalent radius is also much larger than the electron gun to the screen distance. Therefore, the electron beam is scanned