| 摘要 |
PURPOSE:To uniform an electron beam generating in order from all of the electron sources on a picture in a time lapse by detecting a beam current value in a horizontal blanking period,and performing a feedback control so that the beam current value coincides with a prescribed level. CONSTITUTION:A horizontal blanking period beam is cut off with a beam cut off signal 56 impressed on a G4 electrode 16, and flows in an electrode 15', and is taken out as a voltage signal with a current detection part 51, and is inputted to a (-) input terminal in a differential amplifier 52, and a difference between a reference voltage impressed on a (+) input terminal is outputted. The difference against a certain reference in the quantity of the beam current outputted from the differential amplifier 52 is impressed on a G2 electrode 14 as a G2 drive signal 59 through an amplifier 54, and the quantity of the beam current is controlled with the G2 drive signal 59. After an operation is completed, the hold state of a sample holding circuit 53 is generated, and the value of the G2 drive signal 59 is fixed at a certain value, then, a normal picture display can be performed.
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