| 摘要 |
PURPOSE:To provide a copying device wherein the fluctuation range of toner concentration is small by providing a timing control means which shortens the decision cycle of toner concentration rather than a prescribed cycle when the ratio of the dark part of an original image detected by an image ratio detecting means is equal to or exceeds a prescribed value. CONSTITUTION:When a printing button is operated to start copying operation, the original image is prescanned prior to the copying operation. Light quantity from the original surface is measured by a photodiode 20 through mirrors 41, 42 and 43. This information is sent to a microprocesser 200, and the ratio of the light part to the dark part of the original image is decided. When the ratio of the dark part of the original image comes under a condition where toner is rapidly consumed and when this ratio detected by the photosensor 20 is equal to or exceeds a reference value, a toner replenishment timing cycle is controlled to be shortened. |
