| 摘要 |
PROBLEM TO BE SOLVED: To provide a system for forming a high quality image which is excellent in correspondency to change of condition. SOLUTION: There are provided a toner concentration sensor 14a which detects toner concentration of a developer in a developing device 14, a controlling toner image density sensor 16 which detects density of a controlling toner image, and control part 21Y, 21M, 21C and 21K, for respective colors, each of which comprises a toner supply-amount control circuit 22 for controlling the amount of toner supplied to the developing device 14 so that the toner concentration detected by the toner concentration sensor 14a approaches a specified control reference concentration as well as an exposure amount control circuit 23 for controlling the amount of exposure light based on the density of controlling toner image detected by the controlling toner image density sensor 16. |
