| 摘要 |
PURPOSE:To keep print picture density proper by forming a reference latent image for a developing device in an upper side on the outside of that in the lower part and setting a developing area of the developing device in the upper side on the inside of the reference latent image for the developing device in the upper side. CONSTITUTION:A reference image M1 is formed with a color toner in a developing area D5 only for the first developing device on a photosensitive drum 1 by a first optical system 3 and a first developing device 4, and a reference image M2 is formed with a black toner on the inside of said developing area D5 by a second optical system 6 and a second developing device 7. Since the reference image M1 is formed in the developing area D5 only for the first developing device and this area D5 is on the outside of a developing area D2 of the second developing device 7 in the lower side, a magnetic brush having the black toner does not rub the reference image M1 formed with the color toner at the time of development of the second developing device 7. Thus, color mixture is not caused by superposing the black toner the reference image M1 formed with the color toner. |
