| 摘要 |
PURPOSE:To provide a copying machine capable of obtaining optimum image quality corresponding to the kind of original for images requiring gradation, high resolution. etc. CONSTITUTION:In the original requiring the gradation like the image of a photographic style, a first developing mode is set by a developing mode input device 91 and the peripheral speed of the developing roll 4 at the time of developing is set almost the same as that of a photosensitive drum 1. Moreover, an AC bias on which a DC is superimposed or a pulse bias that the time ratio of high and low voltage parts is about 1:1 can be applied to the developing roll 4 as well. On the other hand, in the original requiring the high resolution like the image including many fine lines of a character, a table, etc., a second developing mode is set and the peripheral speed of the developing roll 4 at the time of developing is set higher than that of the photosensitive drum 1. Moreover, a DC bias or the pulse bias that the time ratio of the high and low voltage parts is about 2:3-1:10 (the case of N/P development) can be applied to the developing roll 4. |
