| 摘要 |
PURPOSE:To stabilize a binary coding process, by forming the threshold level for binary coding in accordance with the output of a separately provided line image sensor. CONSTITUTION:Reflected light containing the picture information of a reading line RL is divided into two parts by a half mirror 12 and one part forms its image in a line image sensor 14 for reading out picture signals. The other part forms its image in another line image sensor 16 for detecting the background density. The output of the line image sensor 14 is supplied to the (+) side of a comparator 24 and the output signal of the line image sensor 16 is supplied to the (-) side of the comparator as a threshold signal SB4 after its level is lowered at a prescribed rate. Therefore, a binary signal SV is outputted from the comparator 24 and supplied to the next stage device.
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