| 摘要 |
PURPOSE:To stabilize development effect and to hold it adequately for a long period by detecting the toner density of a developer and by exercising variable control over a level for detecting said toner density according to the density of a reference image formed on a photoreceptor. CONSTITUTION:The toner density of a developer 45 in a developing device 43 is detected by a magnetic permeability sensor 63, whose detection signal is inputted from a developer density detection part 67 to a CPU61. On the other hand, a control signal from the CPU61 causes a laser beam 17 from an A/O modulator 16 to illuminate a photosensitive drum 31, and the image density Dp of a developed reference image obtained by developing a reference latent image by the developer is detected by a reflection density detection part 143, whose detection signal is inputted to the CPU61. Then, the A/O modulator 16 is controlled to read background density Do on a photoreceptor surface 33 after the development, and on the basis of those density levels Dp and Do, a detection level for detecting the toner density is varied. |
