| 摘要 |
An electron gun for producing and directing at least one electron beam along a beam path comprises a beam forming section and a main lens section for focusing the electron beam. The main lens section includes first and second electrodes arranged along the beam path and each having an aperture through which the electron beam is passed, and an auxiliary electrode located between the first and second electrodes and having an aperture through which the electron beam is passed. The aperture of the auxiliary electrode is wider than those of the first and second electrodes. Different voltages are applied to the first and second electrodes, and the auxiliary voltage between the voltages is applied to the auxiliary electrode. An electrostatic field formed between the first and second electrodes is corrected by placing a correcting electrode within the bathtub-shaped auxiliary electrode which is responsive to the auxiliary voltage such that the electron beams are more effectively converged. |
