FLOATING BINARIZATION SYSTEM

PURPOSE:To precisely execute a binarization without receiving the effects such as the unevenness of illumination and the strain of shading, etc., by setting a floating binarization threshold following the waveform in an original signal in the case of binarization of a character pattern and a wiring pattern, etc. CONSTITUTION:When first order differentiation is executed to the original signal (a) so as to compute the absolute value of a differential value, a differential signal (c) is obtained and the projecting part of the waveform in the differential signal (c) is equal to the edge part of the waveform in the original signal (a). A threshold process is executed to the differential signal (c) with a proper differential threshold (d) in order to extract the edge part and a differential binarization signal (e) can be obtained. When the time, obtained by extracting the center of the high level period of the differential binarization signal (e), is t1, the time t1 is equal to the center part of the edge part in the original signal (a). As for a video signal including the strain obtained by image-picking up the character pattern and the wiring pattern, etc., only signal part can be precisely binarized.