| 摘要 |
<p>PURPOSE:To take an accurate measurement even in case of the density variation of the edge of a sheet by setting a predetermined reference value in a detector which recognizes the edge position of the sheet and outputs a video signal. CONSTITUTION:An image sensor 3 outputs the video signal S1 generated by recognizing the edge position of the sheet 2 by a light receiving element 1 and a pulse counter circuit 9 converts the signal S1 from the sensor 3 into the number of pulses corresponding to the actual edge position of the sheet 2. Then a computing element 14 calculates the deviation between the target position of the edge of the sheet 2 and the actual position of the edge of the sheet 2 from the number of pulses obtained by the circuit 9. In this case, the output of the element 1 when the edge of the sheet 2 does not pass between the sensor 3 and a light source 4 is denoted as V1 and a value which is about 10% lower is set as the reference value V3. Here, if the density at the edge varies according to a pattern, the quantity of transmitted light varies, but the reference value V3 is about 10% lower than the value V1, thereby accurately detecting the edge without being affected by the variation.</p> |
