Patent ID: 8345323

Claim:
An image reading lens system comprising, in order from an object side: a positive first lens having a convex surface faces directed to the object side; a second lens, which is a biconcave lens; a third lens, which is a biconvex lens; a positive fourth lens having a convex surface faces directed to an image side; and a negative fifth lens having a convex surface faces directed to the image side, wherein the following conditional expressions (1) and (2) are satisfied: 0.06< D 8/ f< 0.16 (1) 0.77< f 4/ f< 1.81 (2) where f denotes a focal length of the whole lens system, f 4 denotes a focal length of the fourth lens, and D 8 denotes a space between an image side surface of the fourth lens and an object side surface of the fifth lens on an optical axis.