Patent ID: 8654457

Claim:
A wide-angle optical system comprising, in order from an object side to an image side: a front group; a stop; and a rear group, wherein the front group comprises, in order from the object side to the image side, a first lens having a negative optical power, a second lens having a negative optical power, and a third lens having a positive optical power, the rear group comprises, in order from the object side to the image side, a fourth lens having a positive optical power, and a fifth lens having a negative optical power, an opposite surface from the stop of each of a pair of lenses which are arranged at the both sides of the stop is a convex surface, and the wide-angle optical system satisfies the following conditional expressions: 1.7 <νd 4 /νd 3<2.7 (3), 2.43 ≧νd 4 /νd 5>1.5 (4), Ff/Fr> 0 (5), −2 <F 5/ F 4<−1 (7), where νd3 is an Abbe number of the third lens, νd4 is an Abbe number of the fourth lens, νd5 is an Abbe number of the fifth lens, Ff is a focal length of the front group, Fr is a focal length of the rear group, F4 is a focal length of the fourth lens, and F5 is a focal length of the fifth lens.