| 摘要 |
PURPOSE:To obtain a required correction amount by a low applying voltage, by forming a set of quadrupole electrode opposing the first electrode where the openings are cut up upward and downward, and the second electrode where the openings are cut up to the both sides, piling quadrupole electrodes in the two step axis direction to compose a quadrupole electrode, and forming the length of the electrode pieces in the axial direction at required lengths. CONSTITUTION:When a correcting focusing voltage is applied between electrodes 1 and 2, electron beams 20 passing through openings 21, 11, and 21 receive two rounds of corrections by the two quadrupole lenses formed by two sets of quadrupole electrodes 100 and 200. Therefore, since the deflecting aberration may be corrected by the correction amounts of the two quadrupole lenses, a required correction amount can be given to the electron beams 20 by a low applying voltage, resulting in a low cost correction focus power source. In this case, the forms of the openings 11 and 21 of the first and second electrodes 1 and 2 composing the quadrupole electrode 100 may be made in a circular or an oval form, and moreover, numerous sets of quadrupole electrodes 100 may be superposed if necessary.
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