| 摘要 |
PURPOSE:To improve an electron beam spot size at the screen periphery on a screen and improve the resolution by setting the relationship between the lengths and diameters of the second and third grids to the preset values and selecting the applied voltage and anode voltage of the third grid to the preset values. CONSTITUTION:An electron gun is constituted of an electrostatic pre-lens system Lensp provided with a cathode K, the first grid G1, the second grid G2, and the third grid G3 and a main electron lens system LensM. The lengths L2, L3 and the diameters D2, D3 of the grids G2, G3 are selected to L2/D2<=0.3, L3/D3<=1.2, and the applied voltage of G3 is selected to 5-20% of the anode voltage Eb. When the lengths of the grids G2, G3 are shortened, a convex meniscus type electron lens is formed. The overall image multiplication factor is determined almost by the image multiplication factor (m) of the main electron lens. As a result, the beam spot size VSS at the screen periphery is improved, and the resolution can be improved.
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