| 摘要 |
<p>PURPOSE:To reduce the influence of a secular change and to accurately detect a paper sheet by setting a current applied to a reflection type sensor before detection to the best value and correcting the sensitivity of the sensor. CONSTITUTION:A motor 14 is driven to move a carriage and a black reference reflecting plate 1 and the detection sensor 4 are opposed to each other. Then plural kinds of current value data are read out of a ROM 11 and applied to a D/A converter 5 to supply a current iL which increases gradually to a projection part 4A. Then the photodetection output of a photodetector 4B is compared with a threshold voltage VTH successively and current values which are decided as black values are stored in a RAM 12. Then a white reference reflecting plate 2 is opposed to the sensor 4 and current values which are decided as white values are stored similarly. Consequently, the center value of the stored current values is supplied to a projector 4A by reflecting plates 1 and 2 to detect recording paper 3. Thus, the sensor 4 is set to the best sensitivity and stable detection is performed.</p> |
