公开(公告)号：US3614520A

公开(公告)日：1971-10-19

申请号：US3614520D

申请日：1968-09-12

Applicant: FORGFLO CORP

Inventor： COLEMAN JOHN W

IPC: H01J3/02 ,  H01J37/063 ,  H01J37/07 ,  H01J29/58

CPC classification number: H01J37/07 ,  H01J3/029 ,  H01J37/063

Abstract: An electron beam focusing means including a grid cap and accelerating lenses is provided. To permit a small change of voltage on the grid cap to overcome the defocusing effect of a great change in voltage on the accelerating electrodes, a short focal length accelerating lens is positioned in the front focal length of the long focal length lens constituted by the high voltage accelerating electrodes.