| 摘要 |
PURPOSE:To enable continuous use of an automatic let-off mechanism even if a white ground original and a color ground original exist by comparing the detecting level on the white ground side of the original obtd. from a ground color sensor with a reference white level and correcting the developing bias to the white ground side according to the deviation therebetween. CONSTITUTION:The detected output signal corresponding to the ground color density of an original 2 from a ground color sensor 4 provided at the conveying inlet 1D of an automatic let-off mechanism 1 is inputted via an AD converter 5 to a CPU6 and is compared with the data on a reference white level desity and the deviation therebetween is determined. The deviation data is fed via an I/O circuit 7 to a developing bias circuit 8 and the developing bias corrected to the while level side according to the deviation is generated. The color ground part is thus copied to the white level similar to the white ground original. Therefore, even if the white ground original and the color ground original exist mixedly, all the originals are continuously copied at the same ground color density. |
