| 摘要 |
PURPOSE:To prevent a low quality image due to lag of control timing, by detecting density of the toner image of a reference target in order to control image formation conditions, and inhibiting feed of a copying paper alone in case of abnormal toner density. CONSTITUTION:The toner image of a target 3 is detected beyond the copying region of a photosensitive drum 6 to optically detect the toner density with a detector 10, and its value is compared with a reference density value, permitting image formation conditions, such as bias voltage, charging current, exposure quantity, and toner feed to a developing device to be controlled with CPU, and a high quality stable image to be formed. When density of the toner image of the target 3 becomes abnormal, only feed of a copying paper is inhibited, and this inhibition is released when the image formation conditions are further controlled in accordance with the background density as far as it is in the controllable range and the toner image density becomes a prescribed value, thus an image of low quality due to lag of control timing to be prevented. |
