| 摘要 |
PURPOSE:To obtain a picture signal which is not affected by shading or the like, by extracting a signal concerning the background from the picture signal to control a variable gain amplifier which amplifies the picture signal. CONSTITUTION:A picture signal ei is outputted through an amplifier A1 controlled by a gain controlling circuit GC. Meanwhile, the picture signal ei is supplied to a background extracting circuit BP, and a signal eB concerning the background is extracted from the picture signal ei. The signal eB and the picture signal ei are supplied to a comparator COP to output a signal eBO indicating the background section. By this signal eBO, a switch S is turned on for the background section and is turned off for sections other than the background section. Consequently, the amplifier A is controlled to keep a certain level when the switch S is turned on, and the amplifier A is controlled so as to hold the just preceding gain when the switch S is turned off. Thus, the picture signal which is not affected by shading or the like is obtained. |
