Patent ID: 6940661

Claim:
A lens assembly, comprising an aperture, and a lens unit having a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged behind said aperture in sequence, said first lens being a biconvex lens disposed at the front side of the lens unit, said second lens being a biconcave lens, said third lens being positive lens with a surface of facing the image side having a curvature radius larger than the curvature radius of the opposite surface, said fourth lens being a negative meniscus lens and said fifth lens being a positive lens with a surface of facing the image side having a curvature radius larger than the curvature radius of the opposite surface; said fourth lens and said fifth lens being attached together to form a compound lens, said aperture disposed in front of said first lens; wherein said lens unit of said lens assembly has conditions as described hereunder: 0.45< f 1 / f< 0.9 (1) −0.75< f 2 / f<− 0.3 (2) 12< f 5 / f< 20 (3); wherein f 1 is the focal length of said first lens, f 2 is the focal length of the second lens, f 5 is the focal length of said fifth lens and f is the total focal length of said lens unit.