| 摘要 |
PURPOSE:To maintain a fixed image quality regardless of any environmental fluctuation, etc., by switching an exposure quantity based on control information different between when a photosensitive body exposing quantity is increased and when it is decreased. CONSTITUTION:The exposure amount is switched based on the control information different between when the photosensitive body exposing quantity is increased and when it is decreased. For example, at the time of obtaining a required potential contrast of the potential Vc, the exposure quantity is not switched even when the potential contrast becomes the value Vc after once the exposure quantity is switched from a Lo side to a Hi side. It is not until the potential contrast lowers to a value VB lower than the VC that the switching operation is carried out. Thus, even when the potential contrast slightly flactuates because of such as the environmental fluctuation, the exposure quantity is not switched, and therefore, a fixed image quality can be maintained. |
