METHOD AND CIRCUIT FOR AUTOMATIC COMPENSATION OF IMAGE QUALITY

摘要

PURPOSE:To minimize the sensor error due to self heating of a light emitting element while shortening the processing time by measuring the sensor output of the base of a photosensitive body for each sensor output of a toner patch in order to determine one image forming condition and then determining the ratio thereof. CONSTITUTION:A reference toner patch 59 is provided on a photosensitive drum 21 and a light emitting element 51 emits light upon receiving a signal from a master CPU 40. Light reflected on the toner patch 59 passes through a phototransistor 54 and read into a the CPU 40. The CPU 40 varies the outputs from a copy lamp lighting circuit 431 or a charging unit 50 based on a sensor output and produces three new low concentration toner patches. Sensor outputs are read in from the base part of the photosensitive drum 21 and the toner patch part for every patch. Output ratio between each patch and the base of the photosensitive drum is then calculated and the normality thereof is confirmed. If the sensor output ratio is not normal, trouble is displayed and the circuit is reset. In other words, the conditions of patch analysis and image formation are modifies and the image quality is compensated at the time of copying.