| 摘要 |
PURPOSE:To accurately detect toner concentration by detecting the quantity of light reflected on carrier, detecting the spent quantity of the carrier and correcting the detection difference resulting from the spent phenomenon of the carrier at the time of detecting the toner concentration. CONSTITUTION:A device is provided with a 1st measuring means for measuring the quantity of light reflected on developer, a 2nd measuring means for measuring the quantity of light reflected on the carrier in the developer. That means, 1st and 2nd bias power sources 14 and 15 are capable of selectively connecting through a changeover switch 13, then, the voltage of the 1st bias power source 14 is set a little lower than a developing bias so as to prevent the soiling of a sensor window 12. The voltage of the 2nd bias power source 15 is set considerably lower so that the toner may be discharged from the part opposite to a toner concentration sensor on a developing sleeve and only the carrier may remain. The quantity of the light reflected on the carrier is detected and the spent quantity of the carrier is detected and the detection difference resulting from the spent phenomenon of the carrier is corrected at the time of detecting the toner concentration. Thus, the toner concentration can be accurately detected. |
