| 摘要 |
The quantity of light of an optical sensor including a light emission portion and a light reception portion is adjusted through calculation before sheet detection is performed. In order to perform the light quantity adjustment, a voltage to be applied to the light emission portion of the optical sensor is obtained by performing calculation based on a relation between a voltage applied to the light emission portion before the adjustment and an output from the light reception portion before the adjustment. Then, it is judged whether the obtained voltage exists within a predetermined range and, if a positive result is obtained, the light quantity adjustment is ended. Further, a signal requesting the cleaning of the optical sensor is outputted in accordance with a value of the obtained voltage.
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