Patent ID: 8379327

Claim:
A wide angle optical system comprising, in order from an 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 of an object-side surface and an image-side surface of the third lens are aspherical surfaces each of which is shaped to be convex toward the object side in a vicinity of an optical axis and to be concave toward the object side in a vicinity of an outer circumference of the third lens so that refracting power varies with distance from the optical axis, and wherein the following conditions (1)′ and (2) are satisfied: 2.6 <d 2 /d 3 <7 (1)′ −0.04 <f/f 3 <0.04 (2) where d 2 is a thickness of the first lens on the optical axis, d 3 is a space distance between the first lens and the second lens on the optical axis, f is a focal length of the wide angle optical system as a whole, and f 3 is a focal length of the third lens.