Patent ID: 8749893

Claim:
An inner focus lens, in order from an object side to an image side, comprising: a first lens unit having positive optical power; a second lens unit having negative optical power; and a third lens unit having positive optical power, wherein the second lens unit is moved along an optical axis so that focusing from an infinite-distance object side to a short-distance object side is achieved, the first lens unit includes a bi-convex air lens, and the following conditions (1) and (4) are satisfied: 0.65 <|f 2 /f|< 5.00 (1) 0.02 <D 2 /{f ×tan(ω)}<0.30 (4) where, f 2 is a focal length of the second lens unit, f is a focal length of the entire system in an infinity in-focus condition, D 2 is an optical axial thickness of the second lens unit, and ω is a half view angle (°) of the entire system in an infinity in-focus condition.