| 摘要 |
<p>PURPOSE: To enable the amounts of electrons emitted from electron guns to be controlled digitally and stably, to simplify the structure of each electron gun, and to facilitate manufacture. CONSTITUTION: A plurality of electron-emitting elements (micro electron guns) 10 driven at constant current are grouped into groups G1 to G4 of different numbers, and a drive circuit 3 either drives the groups of electron guns individually or selects plural groups for simultaneous driving. Since the amount of electrons emitted from each of the groups G1 to G4 of electron guns is proportional to the number of electron-emitting elements 10 constituting the group, the amount of electrons emitted can be digitally varied.</p> |
