Exposure device having light shading members for correcting light

Abstract

An exposure device for use in a copier having a magnification mode, includes a light source having a uniform non-shaded light distribution characteristic when a predetermined magnification ratio is selected; a lens moving mechanism for focusing an image on a photoreceptor so that a magnification of an image can be changed by movement of a lens while a light shading member is being rotated; a rotatable light shading member which is rotatable about a shaft; and a light shading member rotation mechanism for correcting a light distribution of an image light on a photoreceptor surface relative to a variable magnification ratio of the lens while the light shading member is being rotated. The light shading member includes two thin light-shading plates which have a cross section along the optical path that is unequally varied at adjoining portions thereof when the light shading member is rotated. If two surfaces of the light shading plates are successively placed on the optical path at different angles crossing the optical axis and if the amplification ratios for each of the plates is selected to be larger and smaller respectively than a predetermined ratio, then the shapes projected on a surface perpendicular to the optical axis for each plate are formed so that the light amount distribution on the photoreceptor provided by each plate is made uniform by the light shading member rotation mechanism.