| 摘要 |
PURPOSE:To read the density on a photosensitive drum accurately and obtain a density signal, and to obtain a reliable photodetector, by making an output correction for the staining of the photodetector prior to a copying process. CONSTITUTION:The output of the photodetecting element 3 near the surface of the photosensitive drum 1 is converted by an A/D converter into a digital signal, which is inputted to a CPU6. The output signal 7 of the CPU is utilized as a density control signal for controlling toner density, etc. The density part of the front part of an original is formed on the drum 1 and read by the sensor 4 to control the output of a developing bias, etc., on the basis of the read output. In this case, the CPU6 is stored with the difference between the detection output of the sensor 4 regarding the cleaned drum 1 and the reference density detection output of the density pattern, i.e. reference output difference and the basis of it, the surface stain of the photodetecting element 3 is detected and corrected to perform control, thus obtaining an invariably proper picture. |
