Electrophotographic method and apparatus for providing accurate half-tone images

摘要

An electrophotographic method and apparatus is disclosed which is able to faithfully reproduce the half-tone portion of an original image on a photosensitive medium having an electroconductive layer, a photoconductive layer and an insulating surface layer. The present invention is directed particularly to improvements in the secondary charging step in the above method. According to the invention, the process of secondary charge includes the steps of subjecting the photosensitive medium to the action of corona discharge having the component of opposite polarity to that of the primary charge with simultaneous light image exposure, exposing the photosensitive medium surface to a light image while reducing or stopping the action of corona discharge and exposing the photosensitive medium surface to a light image while controlling the amount of corona discharge.