PURPOSE: To correct centering by utilizing a signal A obtained from an image pickup tube which is a reference of a color camera, a signal B obtained from other image pickup tubes, respective differential signals and their inversion signals and calculating a delay and an advance of the signal B with respect to the signal A.

CONSTITUTION: A signal A obtained from an image pickup tube which is a reference of a color camera is added to a differential amplifier 130 after it is differentiated by a differentiator 110. A signal B obtained from other image pickup tubes is added to a differential amplifier 131 after it is differentiated by a differentiator 111. The signal A and the signal B control a current source 121 of the amplifier 131 and a current source 120 of the amplifier 130. Outputs of a transistor TR118 of the amplifier 131 and a TR117 of the amplifier 131 and those of a TR116 of the amplifier 130 and a TR119 of the amplifier 131 are inputted to OR circuits 126 and 127, respectively. Signals X and Y as shown in equations I and II are obtained in the outputs of the circuits 126 and 127, and centering of the signals X and Y can be corrected as a delay or advance of the signal B with respect to the signal A.