| 摘要 |
PURPOSE:To facilitate an adjustment of the quantity of light incident to a photosensitive drum and to obtain excellent copy density by providing an optical system which guides the reflected light from an original part slightly in front of an original exposure position to a light quantity sensor which detects original density. CONSTITUTION:The exposure light source 1 and density measuring light source 30 of an exposing device are provided separately, and luminous flux from the density measuring light source 30 illuminates a position Q slightly in front of a position P in the original exposed to the light source 1 through an image forming lens 31. Then, the light quantity sensor 32 is arranged under the position Q to measure the density at the position Q. The output of the light quantity sensor 32 is passed through an amplifier 34 and a lamp voltage controlling circuit 35 to adjust the quantity of light from the light source 1. Thus, the quantity of light incident to the photosensitive drum is adjusted to obtain the excellent copy density. |
