Patent ID: 8149524

Claim:
An optical system comprising, in order from an object side to an image side: a first lens unit; an aperture stop; and a second lens unit having a positive refractive power, wherein the first lens unit includes: a first lens subunit having a negative refractive power; and a second lens subunit having a positive refractive power, wherein the first lens subunit includes, in order from the object side to the image side: a first lens having a negative refractive power and having a meniscus shape whose surface on the object side has a convex shape and whose surface on the image side has an aspheric shape; a second lens having a negative refractive power; and a third lens having a negative refractive power, and wherein a focal length of the entire optical system (f), a focal length of the first lens (f 1 l ), and respective radii of curvature of lens surfaces of the second lens on the object side and on the image side (G2R1, G2R2) satisfy the following conditions: −1.6< f 1/ f<− 1.2 0.1<( G 2 R 1− G 2 R 2)/( G 2 R 1+ G 2 R 2)<0.5.