| 摘要 |
PURPOSE:To enable to avoid effectively false signal generation from return beams, by sending return beams in a broad sense to the scanning area by a repeller electrode. CONSTITUTION:A repeller electrode 81, installed at the front of the target side of the electrode 8, has a rotating hyperbora tangent curve surface, forming a cone with half angle 45 deg. near its origin, and a potential equal to or lower than that of the cathode K of the electron gun 2 is applied. Imaglnarily, a return beam 10 from a point P on the axis changes it direction in a decelerating electric field formed by the electrode 81, reaches to a position symmetric to the tube axis from the incident position, changes the direction again, and reaches into the scanning area A of the target 4 as a return beam 11 in a broad sense. Thus, generation of return beam images can be prevented. |
