CAMERA TUBE

PURPOSE:To enable even a compact camera tube to have a high resolution so as to make a television camera compact, by combining a photoconductive film of decreased thickness and increased storage capacity with an electron gun whose electron beam defining aperture is made small to reduce the diameter of a scanning electron beam. CONSTITUTION:An external power supply 10 is connected between a transparent electrode 7 and a cathode 1. A photoconductive film 5 is scanned by a focused and deflected electron beam 2. As a result, the scanned surface of the photoconductive film 5 is negatively charged and has its equilibrium potential is setted nearly to the potential of a cathode 1 resulting the photoconductive film is almost charged by the external power supply. When light comes in, the electric resistance of the photoconductive film 5 drops so that the negative charge is increasingly discharged. As a result, an electric charge pattern corresponding to the quantity of the incoming light is formed on the scanning side surface of the photoconductive film 5, and the potential of the surface varies. When the photoconductive film 5 is scanned by the electron beam 2 at the next period, the electron beam landing occurs corresponding to the variation in the potential of the surface, so that a charging current nearly equal to the quantity of the discharged charge flows through current meter 11. For that reason, an optical image is converted into a time-sequential signal current. The storage capacity of the photoconductive film 5 is set at 15 muF/m to 150 muF/m .