| 摘要 |
PURPOSE:To set a white reference level to a maximum value of a white level following width in advance and to store a picture density quantizing signal of the picture input in this case as the initial value of the white level. CONSTITUTION:When scanning is done and a picture input is given, a many- valued level corresponding to the picture input is outputted, and comparison information whether the picture input is larger, smaller than or equal to the reference level from a D/A converter 5 is given to an ROM2. When larger, 1 is added to the content of a shift register 4, when smaller, 1 is subtracted and when equal no operation is done and then the content of the shift register 4 is updated. The content of the shift register 4 is given to the D/A converter 5 via a gate circuit 7, and applied to an A/D converter 1 as the next white reference level. Thus, the reference level depending on an input signal can be set. |
