| 摘要 |
PURPOSE:To obtain sharp copied pictures irrespectively of the kinds of originals in a copying machine using a one-component developer by controlling the selection of original density-copying density characteristics (gamma characteristics) according to the kinds of originals. CONSTITUTION:A developing biasing circuit is connected to a developing roll using a one-component type developer, and an exposure control circuit is connected to an exposure lamp. Now, the picture copied when the density ratio between the texture of an original such as characters and the contents of the original is large is as shown by a characteristic curve G, and the sharp picture is obtained. However, if, for example, a diazo copy original or the like of the small density ratio is copied, the characteristic curve is H, and the picture which is dark overall is formed. Then, if an original selecting switch is changed over to the photograph side, a developing bias is applied, and the reference voltage of the exposure control circuit is increased by which the point I of the curve H can be moved to the point J and to make a curve K. Therefore, the sharp pictures having no fogs are obtained. |
