| 摘要 |
PROBLEM TO BE SOLVED: To provide an excellent image with time elapsed regardless of the installing environment of a copying machine by detecting the soiling on all of the mirrors and the lenses of an exposure device. SOLUTION: Light reflected on an original 1 is made incident on the lens 11 through the first mirror 13, the second mirror 14 and the third mirror 15 and projected on a photoreceptor 12 through the fourth mirror 16. The half mirror is used for the mirror 16 and the light reflected on the original 1 is used also for irradiating a photodetector 11. Therefore, the deterioration in light quantity caused by the soiling on the mirrors and the lenses is precisely cancelled by increasing the bias of a developing roller 20 with respect to a reference bias value in the image forming device of such a system that the output value of an optical sensor 4 reading a reference density reflection plate 3 at an initial time is compared with the output value read with time and the image is obtained by electrostatically charging the photoreceptor once, for example. |
