| 摘要 |
PURPOSE: To easily correct an instrumental error between a scanner part and a printer part and to improve picture quality by providing a density-density conversion table provided with plural correction curves between the scanner part and the printer part. CONSTITUTION: When copying is started, the light emitting diode LED of an image density sensor DS1 emits light first by increasing the output voltage of a DC power source Vref by every 0.2V from 0V by the control of an MPU 500, and density in which no toner is attached on an image carrier 110 is detected, and the output voltage of a density detection circuit 520 at that time is set at 7V. The output voltage of the power source Vref is fixed when the output voltage is set at 7±0.1V. Such operation is also performed on a density sensor DS2 . In this way, the output change of the sensor DS1 and that of the sensor DS2 can be corrected. In other words, the change f the maximum density due to the change of environmental condition and deterioration in the photosensitive layer of the image carrier 110 can be corrected. Thence, gradation is corrected. The maximum density and the gradation of an appropriate copy image can always be maintained by performing such correction while the warming up of a fixing unit 160 is being performed and at every prescribed number of copies. |
