| 摘要 |
PURPOSE:To realize not only a binary coding of the intermediate gradation but a uniform picture quality even to the variable density of the original, by forming a pair of the adjacent picture element signals of the time-series picture element signals to compare them with the different reference level signals with every picture element and then extracting the multi-gradation binary coded signal. CONSTITUTION:In case the difference between the highest and lowest luminances of the video signal is small like the width F, the amplitude M of the reference level signal is decreased by the gain variable amplifier 15 and in accordance with the width F. Thus the binary coded signal output having an increased contrast is obtained. The contrast is increased by controlling the amplitude of the reference level signal, thus reproducing a high-contrast picture. On the other hand, the amplitude of the reference level signal is decreased in case the DC level is lowered with a small difference of luminance and a dark original surface. At the same time, the DC level sent from the variable power source 16 and to be added by the voltage adder 17 is controlled to a low level to cope with a low contrast and low luminance. Accordingly, a faithful multi-gradation binary coded signal is obtained also in this case, thus realizing a reproduction of a high-contrast gradation pattern. |
