| 摘要 |
PURPOSE:To improve focusing characteristics by forming a groove in the bottom of an electrode in the main lens forming electrode in which holes for passing electron beams in both sides of a central hole are asymmetric shape, and the central hole for passing the electron beam is the elliptic hole, and making an electron lens between the second and the third grids eccentric to carry out the concentration of the electron beams. CONSTITUTION:The third grid 50 in the upper portion is constituted by an elliptic plate, and the central hole 50B for passing an electron beam is an elliptic hole, and respective holes 50A and 50C for passing the electron beams in both sides of the central hole are the holes formed by joining a semicircle in the outside and a semi-ellipse with the same dimension as the central hole 50B in the inside, and the respective centers are arranged with distances S. An elliptic groove 50D with a major axis Dl and a semiminor axis h is provided through the range from the center of the central hole 50B for passing the electron beam to the center of the holes 50A and 50C for passing the electron beams in both sides of the central hole. The fourth grid 60 is also in similar constituent. And an electron lens concerning the electron beams in both sides of the electron lens formed between the second grid 30 and the third grid 40 in the lower portion is constituted in eccentric to carry out the concentration of the electron beams. |
