Patent ID: 6992839

Claim:
A lens system comprising: a diffractive surface, and a first lens unit of a positive optical power, a second lens unit of a negative optical power disposed on the image side of said first lens unit, and a third lens unit of a positive optical power disposed on the image side of said second lens unit, wherein during focusing from an object at infinity to an object at a near distance, said first lens unit is fixed, said second lens unit moves toward an image side, and said third lens unit moves toward the object side, and wherein the following conditions are satisfied: 0.40 <f 1 / f< 0.65, −0.50 <f 2 / f<− 0.25, and 0.40 <f 3 / f< 1.10, where f 1 is a focal length of said first lens unit, f 2 a focal length of said second lens unit, f 3 a focal length of said third lens unit, and f a focal length of the entire lens system.