Patent ID: 8605195

Claim:
An image-taking lens system for imaging light from a subject on an image-sensing element, comprising, from an object side: a first lens element having a positive refractive power; an aperture stop; a second lens element having a negative refractive power and having a concave surface facing an image side; a third lens element having a positive refractive power; and a fourth lens element having a negative refractive power and having a concave surface facing the image side, wherein the following formulae are fulfilled: 0.45 <f 3 /f <0.95 (1) 0.75 <SIL/TL <0.95 (2) 0.3 <r 1 /f <0.45 (3) where f 3 represents a focal length of the third lens element; f represents a focal length of the entire image-taking lens system; SIL represents a distance from an aperture stop plane to an image plane along an optical axis; TL represents a distance from a most object-side lens surface of the image-taking lens system to the image plane along the optical axis; and r 1 represents a radius of curvature of an object-side lens surface of the first lens element L 1 .