| 摘要 |
PURPOSE:To simplify the structure of openings of a main electron lens, by inserting an auxiliary electrode, in which three openings with projecting brims are furnished, into a cylindrical electrode with three broken circle overlapping type opening at its enclosed surface, to form an electrode structure. CONSTITUTION:An enclosed cylindrical electrode 2 is made by furnishing three openings with a diameter larger than the axis to axis distance of the openings, overlapping the openings in a broken-circule-overlapping types 21R, 21G and 21B. On the other hand, an auxiliary electrode 3 is made by furnishing three separate openings 31R, 31G, and 31 b with the projecting brim 31W each, at the enclosed surface 32. Then the auxiliary electrode 3 is inserted to the electrode 2 to form the electrode structures 4 and 4'. Thus, by opposing the electrode structure 4 as a focusing electrode G3 and the electrode structure 4' as an anode G4, a bipotential focusing type main electron lens is composed. Therefore, the process of the electrode structure is simplified, and the accuracy is improved.
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