| 摘要 |
PURPOSE:To make a light quantity constant on the surface to be scanned, by varying a light quantity of a laser light source or a sensitivity of a photoelectric converting element, so as to be in inverse proportion to a reflection factor. CONSTITUTION:A laser driving circuit 2 drives on and off a semiconductor laser 3 by switching transistors 30, 31. This semiconductor laser 3 consists of a light emitting element LD and a photodetector PD, and the light emitting quantity of the light emitting element LD is detected by the photodetector PD and fed back to an optical output controlling circuit 32. The optical output controlling circuit 32 controls a current capacity of a current source 33 and makes the semiconductor laser 3 hold an optical output at a constant value. |
