Patent ID: 6833967
Filing Date: 2004-12-21
Classification: G02B

Abstract:
A lens system comprising:a first lens of negative optical power having a meniscus shape whose convex surface faces a front; a second lens of positive optical power forming a biconvex shape; an aperture stop; a third lens of negative optical power forming a biconcave shape; a fourth lens of positive optical power; and a fifth lens of positive optical power forming a biconvex shape, the first lens, the second lens of positive optical power forming a biconvex shape, the aperture stop, the third lens of negative optical power forming a biconcave shape, the fourth lens, and the fifth lens of positive optical power forming a biconvex shape being disposed in order from the front to a rear, wherein the following conditions are satisfied 0.5<0.8, nd2<1.7, and 0.8<1.0, where DB denotes an interval between the second lens and the third lens, nd2 denotes a refractive index of a material composing the second lens, bf denotes a back focal distance, and f denotes a focal length of an entire system.