READ-OUT OPTICAL SYSTEM

摘要

PURPOSE: A read-out optical system is provided to demonstrate excellent image- formation performance whose chromatic aberration is corrected without increasing the constituting number of lenses by having a diffraction effect on a lens surface. CONSTITUTION: The read-out optical system includes a diaphragm, a first lens and a flat plate optically equivalent to the face plate of an image pickup device which are orderly arranged from an object side. The image side surface of the first lens constituting the read-out optical system is formed into a convex surface, and also a grating element surface having positive refracting power is formed on the image side surface. Also, the object side surface of the first lens is formed into an spherical surface whose partial radius of curvature is made smaller as it goes away from an optical axis.