Patent ID: 7418199

Claim:
An imaging apparatus comprising: a photographing optical system; and an image sensor converting an optical image formed on an imaging surface by the photographing optical system into an electric signal, wherein the photographing optical system consists of, in order from an object side toward an image side, a first lens unit with positive power in which a most object-side lens surface is concave and a most image-side lens surface is convex, an aperture stop, a second lens unit with positive power in which a most object-side lens surface is convex and a most image-side lens surface is concave, and a third lens unit with positive power, wherein air spacing between the second lens unit and the third lens unit assumes a shape of a biconvex air lens, and wherein the photographing optical system satisfies the following condition: 1.4 ≦|r 2 R/IH≦ 15.0 where IH is a maximum photographic image height, which is a half of a diagonal length, in an effective imaging area, of the image sensor, and r 2R is a paraxial radius of curvature of the most image-side lens surface of the second lens unit.