| 摘要 |
PURPOSE:To accurately correct an unevenness in a sesitivity for every dot and to prevent a binarization error by deciding a threshold for every dot of respective main scanning lines based on the peak value of a main and sub- scanning directions. CONSTITUTION:At the time of scanning an the picture of an original, the picture signal level of the main scanning direction is traced by a peak value detecting means 21 to detect the peak value of the main scanning direction for every main scanning line, the picture signal level of the sub-scanning direction is traced to detect the peak value of the sub-scanning direction for every dot and a threshold value deciding means 28 decides the threshold for every dot of the respective main scanning lines based on the peak values of these main and sub-scanning directions. In this case, the peak values of the main and the sub-scanning directions are changed according to the fluctuation in time of the first density or the quantity of light of an original, threshold decided based on the peak value is changed according to the fluctuation in time of the first density or the quantity of the light of the original and the binarization error can be prevented.
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