Exposure correcting device

摘要

A light-shield plate for correcting the ununiform exposure distribution in an original reading apparatus for example a facsimile resulting from so-called cosine fourth power rule is composed of an easily produceable single member having an arc of a radius R and is positioned in front of or behind an imaging lens at an axial distance L from the lens and at a perpendicular distance H from the center of the arc to the optical axis in such a manner as to be parallel to the light beam entering or emerging from the lens corresponding to the longitudinal direction of the illuminated area on the original and as that the amounts L, H and R are selected to satisfy a certain relationship.