| 摘要 |
PURPOSE:To obtain a good focusing electron beam by forming a noncircular electron beam pass hole section having long and short diameters, while providing a shielding board for correcting a noncircular electronic lens in the proximity to the wall section located in short diameter direction. CONSTITUTION:A central electron beam pass hole section 33 and side beam pass hole sections 34, 35 are made along horizontal axis X4-X4' in one row through a main face section 32 of an electrode structure 31, where the diameter of said sections 33-35 is made larger than the distance Sg between the centers of two adjoining beam pass hole sections, while three beam pass hole sections are formed to be one through-hole, and a shielding board 36 is provided at longitudinal central portion of overlapped section of each beam pass hole sections 33-35, together with its departure from main face section 32 by predetermined distance. Consequently, a circular electronic lens having a large diameter is achieved to produce good focusing electron beam. |
