| 摘要 |
PURPOSE:To improve color balance by holding the signal current of a video amplifying circuit at a constant electric current corresponding to fluctuations of the temperature of a face plate. CONSTITUTION:Gain control circuit 5 is constituted by providing variable resistance 6, fixed resistance 7 and temperature compensating element 8. In this constitution, an image pickup signal current increasing corresponding to a rise in the temperature of the face plate has its gain decreased by element 8 having negative temperature characteristics. For this purpose, the signal current obtained from the output terminal of preprocess amplifier 4 is held constant to improve color balance. In this case, a change in output when resistance 6 of amplifier 4 is adjusted is found, an increase or decrease in signal current is converted into a change in resistance value and the resistance value becomes equal to the total value of resistances 6 and 7 and element 8 by selecting the value of element 8, so that the signal current will be held constant. Thus, the color balance can be improved easily by using element 8. |
