Patent ID: 7473905
Filing Date: 2009-01-06
Classification: H01J

Abstract:
1. An electrostatic deflector comprising: a cylindrical support body made of an insulating material; two pillar-like first electrodes disposed opposite to a first vertical plane including an X-axis; two pillar-like second electrodes disposed opposite to a second vertical plane including a Y-axis; 8m pillar-like third electrodes (m=1, 2, 3, . . . ) arranged such that an even number out of the third electrodes are disposed between each one interelectrode space between the four electrodes consisting of the first and second electrodes adjacent pairs of third electrodes defining holes therebetween; holes; and rod-like members mounted in the holes such that the rod-like members are not in contact with any of the electrodes; wherein the (4+8m) electrodes consisting of the first, second, and third electrodes are arranged on the same circumference with gaps therebetween such that a cylindrical form supported by the support body is formed by all of the (4+8m) electrodes; wherein the first and second electrodes are identical in shape and size; wherein the even number of third electrodes are identical in shape and size; wherein alternate ones of the electrodes are used as X-direction deflection electrodes; wherein the remaining ones of the electrodes are used as Y-direction deflection electrodes; wherein spaces formed on both sides of each one of said first electrodes have bent portions that are symmetrical with respect to the first vertical plane; wherein spaces formed on both sides of each one of said second electrodes have bent portions that are symmetrical with respect to the second vertical plane; wherein some of said third electrodes are arranged symmetrically with respect to a third vertical plane including an axis located in an angular position spaced from the X-axis by 45°; wherein the remaining ones of said third electrodes are arranged symmetrically with respect to a fourth vertical plane including an axis located in an angular position spaced from the X-axis by −45°; wherein said holes are formed each across the third or fourth vertical plane and extend the same distance into each of the two electrodes located adjacent to the third or fourth vertical plane; and wherein the deflector itself constituted by the electrodes, the spaces, the rod-like members, and the support body is symmetrical with respect to said first, second, third, and fourth vertical planes.