Image forming device of copying apparatus of the variable duplicate size

Abstract

In copying apparatus capable of producing a duplicate from an original differing in size from each other, a lens is moved when the size of a duplicate to be made from an original is to be changed. When the lens is moved along its optical axis, no change is caused to occur in the distribution of the volume of light passing through the lens for exposing an image forming surface to an optical image of the original. However, in case the original is set such that one side thereof is located on a reference position, the lens is moved in a direction perpendicular to its optical axis, with the result that a lack of uniformity will arise in the distribution of the volume of light thrown on the image forming surface through the lens. Shield means extending from outside the optical axis toward the optical axis is mounted between the original and the lens to cut off a portion of the light flux thrown on the image forming surface to thereby eliminate the lack of uniformity in the distribution of the volume of light thrown on the image forming surface which would otherwise occur.