PURPOSE: To secure such a focusing electrode that is no fear of any slippage occurrence in its focusing point in an easy manner and in a way of highly assembling accuracy, by forming the electrode in a state of what a burring die, a burring bottom hole and a burning punch are all being decentered one another, while providing a cylindrical tilting part with a curved concave part.
CONSTITUTION: For example, an opening 122a at the side of a high potential side electrode 12 is concentrically provided with a cylindrical screening plate 123a having an almost equal inner diameter with the diameter of this opening 122a, and this screening plate 123a is made up in a shape being cut after forming a curved concave part 124a by making a cylinder slant so as to cause the length of its side wall to be successively increased toward a beam's focusing direction. Like this, each of curved concave parts 114a, 114c, 124a and 124c are set up, by making the cylinder slant to each of center axes 4a and 4c, on screening plates 113a and 113c of a low potential side electrode 11 and screening plates 123a and 123c of the said high potential side electrode 12. With this, unevenness in a focusing point converged defectively at one point on an electron beam's shadow mask can be checked to the extent of almost nothing.
MATSUDA KENICHI
YABE MINORU
MAJIMA KAZUO
| JPS5169359A | 1976-06-15 |