| 摘要 |
PURPOSE:To correct and minimize a magnification error at all times even if environment is changed by controlling a basic clock according to the difference between the time of the scanning of a scanned body in a main scanning direction and a reference scanning time. CONSTITUTION:An arithmetic circuit 15 inputs luminous flux detection signals from sensors 8 and 9 and calculates the scanning time of the scanning of the scanned surface 7 with luminous flux from image formation optical systems 5 and 6 in the main scanning direction by using the time difference between those luminous flux detection signals. A ROM 16, on the other hand, is stored with the reference time of scanning of the scanned surface 7 with the luminous flux from the image formation optical systems 5 and 6 in the main scanning direction previously, and the arithmetic circuit 15 compares the real scanning time calculated from the luminous flux detection signals from the sensors 8 and 9 with the reference scanning time stored in the ROM 16 to calculate the difference. Then one kind of basic frequency which minimizes the magnification error among plural kinds of basic frequencies stored in the ROM 16 is selected and read out to control the basic clock, thereby correcting the magnification error of the scanning optical device. |
