| 摘要 |
PURPOSE:To obtain an accurate measured value, supply a necessary amount of toner, and maintain stable development characteristics by measuring image density without charging a photosensitive drum elecrostatically. CONSTITUTION:The photosensitive drum 1 is rotated at a zero potential in a dead cycle before a copying cycle until it faces to a developing device 3 without forming any path latent image on a platen on the drum 1 by exposure, charging the drum 1 by a charging corotron 2, and exposing the patch image. Synchronously, the bias potential of a developing roll 3' is switched from a normal potential to a negative potential and the beltlike latent image corresponding to its duration is formed on the drum 1 and developed into a visual image. The optical density is measured by a sensor 8 arranged in a successive rotational direction and its output is inputted to a comparator 9 and compared with a density reference value to send the output to a motor driving circuit 10 according to the comparison result. Consequently, the driving motor 12 of a toner supplementing device 11 is driven to supply a necessary amount of toner into a developing device 3. |
