| 摘要 |
PURPOSE:To enable the stable concentration controlling of the developer of high accuracy by radiating light to the powder developer composed of carriers and toners and detecting the change in the spectral characteristics of the reflected light thereof thereby performing toner concentration controlling. CONSTITUTION:Since the spectral characteristics of the reflected light from the developer 3 in a developing device body 2 changes according to the mixing ratios of carriers and toners, the change in the spectral characteristics is detected by a photo detector 15. The photo detector 15 comprises incorporating two photo diodes PD1, PD2 of different spectral sensitivities in one package. Based on the output signals of the photo detector 15, concentration signal corresponding to the toner concentration is fetched from a concentration detecting circuit 36 and this concentration signal is compared with the reference concentration signal by a comparator 37. Based on the compared results, a motor 10 is driven to move a toner replenishing roller 9 and replenish toners from a toner containing box 8, whereby the concentration of the developer 3 is controlled. |
