Patent ID: 8649114

Claim:
An imaging optical lens system, in order from an object side to an image side comprising three lens elements with refractive power: a first lens element with positive refractive power having a convex object-side surface at a paraxial region; a plastic second lens element with negative refractive power having a convex or flat object-side surface at a paraxial region and a concave image-side surface at a paraxial region, and both the object-side surface and the image-side surface being aspheric; and a plastic third lens element with negative refractive power having a concave object-side surface at a paraxial region, the shape of the image-side surface thereof changing from concave when near an optical axis to convex when away from the optical axis, and both the object-side surface and the image-side surface being aspheric; wherein the lens elements having refractive power in the imaging optical lens system are the first lens element, the second lens element and the third lens element; wherein a curvature radius of the object-side surface of the second lens element is R 3 , a curvature radius of the image-side surface of the second lens element is R 4 , a focal length of the third lens element is f 3 , a focal length of the second lens element is f 2 , and they satisfy the following relations: 0<( R 3 −R 4)/( R 3 +R 4)≦1.0; and 0 <f 3 /f 2<3.0.