Abstract: A television camera comprising a control circuit for controlling the electron beam current intensity in a pick-up tube which has a current-controlled electron gun, for example a diode gun. The control circuit comprises a controllable current source an output of which is connected to the anode of the diode gun, which anode acts as a control electrode, and a control input of which is coupled to a pick-up tube output for producing a picture signal. In order to obtain a dynamic additional focussing of the electron beam when an electrostatic focussing means is employed the cathode of the electron gun is connected to a voltage source via a, for example, variable resistor.

Abstract: In order to avoid picture disturbances by electric charging phenomena on the tube wall in a camera tube in which no target material is present on the inner wall of the cylinder tube, the tube wall is provided with a surface potential stabilizing material between the window connection and the mesh electrode of the camera tube. This stabilization can be realized by way of a local cover layer having the desired electric conductivity or secondary emission properties, or by locally adapting properties of the glass of the tube wall thereto.