| 摘要 |
PURPOSE:To precisely judge the stain of an original holding member and to prevent the stain of field by detecting the density of the original holding member with an optical detection means and detecting the stain of the original holding member with a stain detecting means based on the level of the detection signal. CONSTITUTION:The optical detection means and the stain detecting means provided opposite to the original holding member are provided, and the optical detection means detects the density of the original holding member and the stain detecting means detects the stain of the original holding member based on the level of the detection signal. Namely, in the case of preliminary scanning, an original 1 and a pressure plate sheet 3 is illuminated when a scanner unit 4 moves back and forward and the reflected light enters one end parts of optical fibers 12-14. Another end parts of the optical fibers 12-14 are optically combined with light receiving elements 15-17 consisting of photodiodes, which generate output current corresponding to the alternation of the quantity of light beams from the optical fibers 12-14. Thus, the stain of the original holding member can be precisely judged and the stain of field, etc., can be removed.
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