| 摘要 |
PURPOSE:To prevent the variance in a video signal of an original material from appearing at gradation data by providing a converting range control means. CONSTITUTION:An inputted video signal includes a fine variation due to unevenness of the surface of the original. Then an object range limit means 1 limits the range being an object of A/D conversion to a prescribed value Vmax to eliminate the variance from the digital signal being an output signal. As the limit method of the A/D conversion object range by the object range limit means 1, there are two methods; one is to control the converting range Vconv of the A/D converter 2 and to bring the variance (v) included in a video signal 3 to the outside of the converting range of the A/D converter 2 and the other is to clamp the video signal itself to a VL, to eliminate the variance (v), thereby preventing the input to the A/D converter 2. Thus, the variance is eliminated and the gradation data of the original surface becomes a constant value and disturbance in the gradation data due to unevenness of the surface of the original is eliminated.
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