ELECTRON GUN HAVING CYLINDER WITH FOCUSING ASSIST PATTERN FOR EASE OF FOCUSING AND DISTANCE MEASUREMENT

摘要

PURPOSE: An electron gun is provided to allow for ease of focusing and distance measurement by using a dummy pattern for focusing formed on a surface of a cylinder cap. CONSTITUTION: An electron gun comprises a cathode gun tip for emitting electrons; a Wehnelt cylinder for supporting the cathode gun tip; a focusing assist pattern formed on a surface of a cylinder cap so as to be used in a measurement of distance between the cathode gun tip and an anode; and the anode arranged in an electron beam exit direction. The size of the focusing assist pattern is determined on the basis of resolution of optical microscope for measuring the distance between the cathode gun tip and the anode.