| 摘要 |
PURPOSE:To suppress the generation of a false signal resulting from a return beam so as to produce high quality images by preventing any adverse effect from being caused by axial shift or welding splush by unifying the central hole electrode with the third grid. CONSTITUTION:A third grid 3' has a bowl-like shape consisting of a unified body of a cylindrical electrode 3a and an electrode 3c which has a central electron beam hole 3b. Therefore, the center of the electrode 3c can be made to coincide with the center of the inner diameter (D3) of the cylindrical electrode 3a with high accuracy, thereby preventing any adverse effect caused by axial shift. Furthermore, because the electrodes 3a and 3c are unified together, it is not necessary to fix them together by welding. Therefore, splush which might be caused by welding is prevented, thereby achieving improved image quality. |
