Patent ID: 8441744

Claim:
An optical image system comprising, in order from an object side to an image side: a first lens element with positive refractive power and having a convex object-side surface; a second lens element with positive refractive power; a third lens element with negative refractive power and having a concave object-side surface and a convex image-side surface, wherein the third lens element is made of plastic material, and the object-side surface and the image-side surface of the third lens element are aspheric; and a fourth lens element with refractive power and having a concave image-side surface, wherein the fourth lens element is made of plastic material, an object-side surface and the image-side surface of the fourth lens element are aspheric, and the fourth lens element has at least one inflection point formed on at least one of the object-side surface and the image-side surface thereof; wherein when a focal length of the optical image system is f, a focal length of the first lens element is f 1 , a focal length of the second lens element is f 2 , a central thickness of the second lens element is CT 2 , an axial distance between the second lens element and the third lens element is T 23 , a curvature radius of the object-side surface of the third lens element is R 5 and a curvature radius of the image-side surface of the third lens element is R 6 , the following relationships are satisfied: 0.5 <f/f 1<1.5; 0 <f/f 2<1.0; 0.2 <CT 2 /T 23<1.1; and −0.65<( R 5 −R 6)/( R 5 +R 6)<−0.05.