| 摘要 |
PURPOSE:To detect the ground density of an original exactly and effectively with a light quantity detector, by providing a light path changing member in an exposure light path from the original to a photoreceptor surface to change the path of part of the light. CONSTITUTION:In exposure light path from an original to the surface of photoreceptor 1 light path changing member 11 is provided consisting of a mirror, prism, or the like for changing the path of part of the light. In the focusing position of light path 13 changed with member 11 light quantity detector 12 is installed. Member 14 is a stopping down plate. Most of the light obtained in accordance with the original is used for exposure of photoreceptor 1, and very small part of the light undergoes cource change by member 11 and forms a focus on detector 12, and the ground density of the original is detected by detector 12 from this small image focused thus. |
