| 摘要 |
PROBLEM TO BE SOLVED: To provide an image forming device capable of precisely detecting the concn. of toner in a developing unit incorporating a developer whose toner concn. can not be detected by an optical ATDC (the system of detecting the toner concn. based on the intensity of reflected light) and supplying a necessary amount of toner, even if the image forming device is provided with this developing unit. SOLUTION: In the image forming device for forming a full color image with four colors of cyan, magenta, yellow and black, an optical sensor 43C is attached to a cyan developing unit 41C, to control the toner concn. by the optical ATDC. On the other hand, in a black developing unit 41Bk, the toner concn. is controlled by AIDC (image density control). The standard developing efficiencyηSTD of the cyan developing unit 41C obtained with the results of the AIDC is compared with the developing efficiencyηof black toner, to decide the supplied toner quantity of the black developing unit 41Bk from the level comparison and supply the toner. |
