Television camera tube with control diaphragm

Claim 1

A television camera tube comprising an electrically conductive transparent layer, a layer of photoconductive material on said electrically conductive layer on which a potential distribution is formed corresponding to an optical image projected thereon through said electrically conductive transparent layer, an electron gun spaced from said photoconductive layer for producing an electron beam for scanning the surface and periodically reducing said potential distribution to cathode potential of said photoconductive layer remote from said electrically conductive layer, said electron gun having a cathode, a grid and an anode, said grid and anode each having an aperture 0.6 mm therein and being spaced apart 0.25 mm for forming an electron beam having a cross-over therebetween, said anode having a second aperture diameter at the area of the smallest cross-section is a maximum of 0.150 mm and a minimum equal to the electron beam diameter at said area for intercepting returning electrons from the photoconductive layer whereby the beam cross-over formed between the cathode and anode can serve as the object to be reproduced, a hollow cylindrical electrode between said anode and said photoconductive layer, and a diaphragm in said hollow cylindrical electrode having an aperture the diameter of which at the area of the smallest cross-section is a maximum of 10% of the distance between the aperture in the anode and the aperture in the diaphragm said aperture diaphragm distance being 12 mm, and the cathode-grid distance being 0.1. mm.