| 摘要 |
PURPOSE:To prevent a decline in picture density even if a sensor is contaminated with toner, by providing a means which controls the light emitting quantity of the light emitting element of the sensor in accordance with the contamination of the sensor at the timing before picture formation immediately after starting copying operations. CONSTITUTION:A sensor 17 inputs the reflectivity data (density data) of the no-picture forming area C of a photosensitive drum 9 at the timing t1 before a patch picture B section and picture forming area D are reached immediately after starting copying operations. Then the input reflectivity data are compared with a 1st sensor correcting standard data and sensor correcting data corresponding to the difference between the two data is sent to a DA converter. The data is converted into an analog voltage and used for the correction. If the sensor 17 is contaminated, the reflectivity data of the no-picture forming area C becomes lower and a difference is produced between the data and the 1st correcting standard data. Therefore a decline in reflectivity corresponding to the contamination of the sensor is compensated. |
