Patent ID: 7394602
Filing Date: 2008-07-01
Classification: G02B

Abstract:
1. An optical system for taking image comprising three lens elements with refractive power, from the object side to the image side: a first lens element with positive refractive power having a convex front surface and a concave rear surface, the front surface of the first lens being aspheric; a plastic second lens element with negative refractive power having a concave front surface and a convex rear surface, the front surface and the rear surface of the second lens being aspheric; a plastic third lens element with positive refractive power having a convex front surface and a concave rear surface, the front surface and the rear surface of the third lens being aspheric; and an aperture stop located between the first lens element and the second lens element for controlling brightness of the optical system; wherein a focal length of the first lens element is f1, a focal length of the second lens element is f2, a focal length of the optical system is f, and they satisfy the relations: f/f1>0.95, |f/f2|>0.34.