Patent ID: 8310770

Claim:
A photographing optical system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface; a second lens element with negative refractive power having a convex object-side surface and a concave image-side surface, at least one of the object-side and image-side surfaces thereof being aspheric; a third lens element having the object-side and image-side surfaces thereof being aspheric, at least one inflection point formed on the object-side surface and the image-side surface; and wherein the photographing optical system further provides a stop and an electronic sensor for image formation, the stop is disposed between an imaged object and the first lens element, there are three lens elements with refractive power; and wherein a radius of curvature on the object-side surface of the first lens element is R 1 , a radius of curvature on the object-side surface of the second lens element is R 3 , a focal length of the photographing optical system is f, a focal length of the second lens element is f 2 , an Abbe number of the first lens element is V 1 , an Abbe number of the second lens element is V 2 , a distance on the optical axis between the stop and the electronic sensor is SL, a distance on the optical axis between the object-side surface of the first lens element and the electronic sensor is TTL, and they satisfy the relations: 0.20< R 1/ f< 1.00; 0.30< R 3/ f< 1.20; 30.5< V 1- V 2<40.0; 0.90< SL/TTL< 1.20; and −0.45< f/f 2≦−0.23.