High resolution electron gun

A high-demagnification electron gun with a small spot size was developed by deflecting the electron beam before it enters a large focusing lens. The pre-focusing deflection allows close spacing between the focusing lens and the tube screen. The diameter of the focusing lens is large compared with the beam deflection to keep spot distortion at a minimum. Either electrostatic or magnetic focusing can be used. For the electrostatic gun with an accelerating lens, only small deflection fields are required since a low voltage beam is to be deflected in the accelerating field. Magnetic deflection is used.