Patent ID: 8072696

Claim:
A wide angle optical system comprising, in order from the object side, an aperture stop, a first lens with positive refracting power, a second lens with negative refracting power, and a third lens, wherein both surfaces of the third lens are an aspherical surface in which refracting power varies in accordance with distance from the optical axis in such a way that the both surfaces have a convex shape facing toward the object side in the vicinity of the optical axis and have a concave shape facing toward the object side in the vicinity of the outer circumference, and the following conditions (1) and (2) are satisfied: 0.1< d 5 /d 6 <0.65â€ƒâ€ƒ(1) âˆ’0.04< f/f 3 <0.04â€ƒâ€ƒ(2) where d 5 is a space distance between the second and third lenses on the optical axis, d 6 is the thickness of the third lens on the optical axis, f is a focal length of the whole of the wide angle optical system, and f 3 is a focal length of the third lens.