| 摘要 |
PURPOSE:To obtain an image with adequate density stably for a long period by comparing the image density of a reference image with a preset value and by varying a reference level for detecting the volume of a developer on th basis of said comparision result. CONSTITUTION:The toner density of a developer 45 in a developing device 43 is detected by supplying a signal from a developer volume sensor 63 to a developer volume detection part 67, whose detection signal is inputted to a CPU61. The sensor 63 is provided with three detecting elements, whose detection reference levels are switched selectively by a changeover switch as a reference one. On the other hand, image density which corresponds to a reference image formed on a photoreceptor 31 is detected by a reflection density detection part 143, whose detection signal is supplied to the CPU61, which controls and sets the detection level of the sensor 63 according to the detection level to supplement the developer containing toner on the basis of a volume detection level. |
