| 摘要 |
PURPOSE:To set the density of a copy image to a desired level by detecting the light quantity of an exposing light from a plate document or an original, and controlling the light quantity or a developing bias voltage applied to a developing device provided in the vicinity of an image carrying body, based on a detecting signal. CONSTITUTION:The titled copying device has a regular original copying mode for placing an original on an original platen and copying it, and a plate document copying mode for projecting an image of a plate document to an image reading position on the original platen and copying it. A light quantity detector S is arranged in an optical path of an image light radiated to a photosensitive drum. A detecting signal of the detector S is inputted to a control circuit 20 through an A/D converter 19. The circuit 20 compares it with a reference light quantity level which has been set in advance, executes a control so that the light quantity of a lamp 4 for illuminating a plate document becomes a reference value, in the case of plate document copying, and also, controls a developing bias voltage applied to a developing device 25. Moreover, in the case of original copying, in the same way, the light quantity of the lamp 6 is controlled, and also, the developing bias voltage applied to the developing device 25 is controlled. In such a way, the density of a copying image can be set to a desired level. |
