| 摘要 |
PURPOSE:To reduce the stain on the light-projected end surface of an optical scanning device and to simplify the circuit constitution and the controling system of the optical scanning device, by forming a picture for controlling the picture density on a conductive member provided on the area which is not scanned by the optical scanning device on a photoreceptor by utilizing reversal development. CONSTITUTION:When an area B of a photoreceptor charged uniformly is exposed in normal development, its electric potential on the surface is made as expressed by a figure. When the electric potential V of a developing electrode is lowered, a toner negatively charged is electrostatically attracted to areas A, C of the photoreceptor and positive-positive development is performed. On the contrary, the electric potential of a surface photosensitive layer 17a of a photoreceptor 17 is made as expressed by the figure in several development, but when bias is applied to a developing electrode 13 from a power source E and its potential V is made to the value close to the potential V of the areas A, C, an electric field of a developing electrode 18 and the photoreceptor 17 is attained as an arrow and a toner charged positively is electrostatically attracted only to the area B and positive-negative development is performed. |
