Patent ID: 8625207

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)′, (2) and (3) are satisfied: 2.6 <d 2 /d 3 <7 (1)′ −0.04 <f/f 3 <0.04 (2) 0.30 <h m7 /h P7 <2.0 (3) 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, f 3 is a focal length of the third lens, h m7 is a shortest distance between the optical axis and a point on the image-side surface of the third lens through which a light ray passing through a center of the aperture stop at an angle of 36 degrees to the optical axis passes for image formation, and h P7 is a shortest distance between the optical axis and a most image-side point on the image-side surface of the third lens.