| 摘要 |
PURPOSE:To detect the size of a unfixed form original accurately and to prevent toner from being wasted by removing charges of a photosensitive body partially according to original size detected on the basis of detection signals of end parts of an original which are obtained by moving a photoelectric sensor. CONSTITUTION:The photoelectric sensor 42 while is driven by a servomotor 40 to move in an X direction is driven by a stepping motor 46 to move in a Y direction, scanning the original optically. The original 15 is placed on an original platen 14 so that one side is at a home position A, and the photoelectric sensor 42 moves in the X and Y directions by tracking points A B C D A in order. At this time, the movement distance from the point A to the point B is calculated by counting pulses generated by the servo motor 40 to calculate the lateral length L1 of the original 15. When the photoelectric sensor 42 draws a track from the point C to the point D, on the other hand, the longitudinal size L2 of the original 15 is calculated from the movement distance from the detection point C' of the lower side end part of the original 15 to the detection point D' of the upper end part. Then, electrostatic charges at an unnecessary part are removed on the basis of the original sizes L1 and L2. |
