| 摘要 |
PURPOSE:To obtain sharp images of high quality rapidly at all times by changing the quantity of the coronas applied upon a photoreceptor according to the kinds of originals thereby changing the potential curve of the latent images from a black color original which is a reference up to a white color original. CONSTITUTION:At the time of forming latent images on a photoreceptor 1 by exposing images thereto by the DC coronas from the 1st corona discharger 2 and the AC coronas from the 2nd corona discharger 3 then irradiating the entire surface with a lamp 4, a potential sensor 10 is provided on the lower stream of the corona discharger 3, and the latent image potential of the photoreceptor 1 in the state that the original exposure lamp is held put out and the latent image potential corresponding to the white color original are measured. These measured values are fed back to a control part 11 and the currents to be applied to the dischargers 2, 3 are thereby changed in order to form the latent images based on the preset potential curve depending upon the kinds of the originals on the photoreceptor 1. In this way, the originals having varying densities or having colors on the background to make photographic fog easy to occur are copied always sharply despite the change in environmental atmosphere or the change in the photosensitive characteristics of the photoreceptor 1. |
