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(11) | EP 0 517 146 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Electron source drive device employing an improvement of an electron source unit |
| (57) Further automatic control systems (11 and 31, look at Fig. 3 and Fig. 6) are described
to keep constant potential differences between the cathode (1) and the conductive
member (3) or the cathode (1) and a second conductive member (30, look at Fig. 6),
respectively. These automatic control systems (11 and 31) maintain constant brightnes.
The system (31, look at Fig. 6) detects external noises. In an electron source drive device, a cathode support member (6) arranged in contact with a cathode (1) is constructed by a conductive member (3) and an insulation member (2) interposed between the conductive member (3) and a contacting portion of the cathode, and the insulation member (2) is made of a material having a resistivity and a specific dielectric constant such that the electric discharge time constant τ of electrons on the surface of the insulation member depending on the insulation resistance and the electrostatic capacity between the surface of the insulation member and the conductive member is set in a visually permissible range of not too much in excess of one cycle of emission Tf of the cyclical electron from the cathode without bringing forth intermittent electron emission. |