| 摘要 |
PURPOSE:To obtain an excellent signal by switching a constant to a positive value when the level difference of three adjacent picture elements is small and the constant into a negative value adequately when the level difference is large to equalize and correct the unsharpened picture signal due to the scanning system. CONSTITUTION:An A/D converter 24 quantizes an analog picture signal 201 subjected to line sequential scanning and converts it into the 1st multi-value digital picture signal 202. The 1st and 2nd picture delay circuits 25, 26 output the 2nd, 3rd multi-value digital picture signals 203, 204 delaying respectively the signal 202 by one picture element's share. The 1st logical circuit 27 inputs signals 202-204 and outputs a 4-bit digital signal 205 having a value expressed in the equation. When the level difference of signal values a0-a2 of the signals 202- 204 is small, a value (k) is switched to a positive value and when the level difference is large, the value (k) is switched to a negative value adequately. Thus, document information is reproduced with fidelity without emphasizing a noise signal with less amplitude to obtain an excellent picture quality.
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