Device for the automatic beam optimization for a picture analyser tube with diode gun, and television camera with such a device

摘要

Device with diode gun, the diode gun (2, 3) emitting an electron beam for recharging a photo-conductive target (6), comprising: - a regulating device (R2, 19, 16) regulating the intensity Ik of the cathode current to a setpoint value; - an adjustable generator (G2) furnishing a first constant setpoint value corresponding to the required beam current at target (6) level in order to recharge it when the illumination is twice the nominal illumination; - a device (P1, 17) furnishing a second setpoint value dependent upon the value Vc of the video signal furnished by the target (6); - a threshold switching device (18) furnishing the regulating device with: either the first setpoint value, when the value of the video signal furnished by the target (6) is below a fixed threshold value Vcs, or the second setpoint value when the value of this video signal is above the threshold value Vcs; the threshold value corresponding to an illumination twice the nominal lumination. Application to television cameras. IMAGE