Patent ID: 7212354

Claim:
A lens system comprising: a first lens element being biconvex, and including a first aspheric surface and an opposite second aspheric surface, the first lens element being made of glass, the first lens element having a refractive index n and a dispersion coefficient v which satisfy the following requirements: 1.65<n<1.75, 50<v<60; a second lens element being concavo-convex, and including a third aspheric surface and an opposite fourth aspheric surface, the third aspheric surface facing the second aspheric surface, the second lens element being made of plastic, the second lens element having a refractive index n and a dispersion coefficient v which satisfy the following requirements: 1.55<n<1.65, 25<v<35; and a third lens element being convexo-concave, and including a fifth aspheric surface and an opposite sixth aspheric surface, the fifth aspheric surface facing the fourth aspheric surface, the third lens element being made of plastic, the third lens element having a refractive index n and a dispersion coefficient v which satisfy: 1.49<n<1.55, 55<v<60.