Patent ID: 6900947

Claim:
An imaging lens device comprising: a zoom lens system which comprises a plurality of lens units and changes gaps between the lens units to thereby generate an optical image of an object which can be optically and successively zoomed in and out; and an imaging sensor which converts an optical image generated by the zoom lens system into an electric signal, wherein the zoom lens system comprises, from the object side: a first unit having a negative power, a second unit having a positive power, the second unit having a cemented lens element joining three lens elements, and a lens element having a positive power, a third unit having a positive power, and an aperture stop disposed between the first unit and the second unit, wherein among the three lens elements which form the cemented lens element, a lens element disposed on the object side directs a convex surface toward the object side while a lens element disposed on the image side directs a concave surface toward the image side, and wherein the following condition expressions are satisfied: −0.2<( R 21 −R 24)/( R 21 +R 24)<1.0 0.6 <R 21/ Fw< 10.0 0.0 ≦h 2/ ha 4<1.0 where R21: a paraxial radius of curvature of the object side-lens surface of the cemented lens element, R24: a paraxial radius of curvature of the image surface side-lens surface of the cemented lens element, Fw: a focal length of the overall system at the wide-angle end, ha4: a distance from an optical axis of an intersection of a principal ray which is at 0.8× of a maximum half-angle of view ω at the wide-angle end and the image surface side-lens surface of the cemented lens element, h2: a distance from an optical axis of an intersection of the principal ray which is at 0.8× of a maximum half-angle of view ω at the wide-angle end and the outermost lens surface of the second unit toward the object side, and where the principal ray is a ray which propagates on the center of the aperture stop.