| 摘要 |
PURPOSE:To eliminate ground stains by detecting the density of the original before it is subjected to exposure lighting and applying the bias potential corresponding to that density. CONSTITUTION:An original 10 is detected of its density by a detector 14 while it is passing. the quantity of the transmitted or reflected light detected by the detector 14 is operated by a density detecting circuit 26 and is changed to an electric signal as a coefficient of transmission or reflection. This signal is stored for the necessary time from the time when it is detected until the time when bias potential is output to a developing device 22, by a density detection value memory device 27. The bias potential of the developing device 22 is set by a bias potential setter 28 and the required bias potential is applied to the developing device 22 at the specified time by a bias potential outputting device 29. |
