Imagery lens system

Abstract

An imagery lens system for image reading consists of first to fourth lens elements which are arranged in this order from the object side. The first and fourth lens elements respectively are double-convex lenses, and the second and third lens elements respectively are double-concave lenses. The following formulae are satisfied. 0.35<f1/f<0.51--(1) 0.34<f4/f<0.45--(2) 0.11<d7/f<0.16--(3) 0.29<d/f<0.41--(4) wherein f represents the synthetic focal length of the overall lens system, f1 represents the focal length of the first lens element, f4 represents the focal length of the fourth lens element, d represents the axial surface separation between the object side face of the first lens element and the image side face of the fourth lens element and d7 represents the central thicknesses of the fourth lens element.

Dependencies are inferred from the claim text.