Patent ID: 8654456

Claim:
A photographic optical system having a plurality of lens units, in order from an object side to an image side and arranged along an optical axis thereof, comprising: a first lens unit having a positive refractive power; a second lens unit having a positive or negative refractive power; and a third lens unit having a positive or negative refractive power, wherein the first lens unit consists of a first lens sub-unit having a positive refractive power and a second lens sub-unit having a positive or negative refractive power with a largest air space provided therebetween, wherein the first lens unit further includes a diffractive optical element and an aspheric surface, wherein the second lens unit is configured to move along the optical axis to effect focusing, and wherein, when L is a length on the optical axis from a lens surface furthest on the object side of the first lens sub-unit to an image plane of the entire photographic optical system, d 1 ab is an air space between the first lens sub-unit and the second lens sub-unit, f 1 a is a focal length of the first lens sub-unit, f 1 b is a focal length of the second lens sub-unit, fDOE is a focal length of the diffractive optical element by only a diffractive component, f is a focal length of the entire photographic optical system, and Fno is an F-number of the entire photographic optical system during focusing on an infinitely-distant object, the following conditions are satisfied: 0.0500< d 1 ab /( L×F no)<0.2000 −1.000< f 1 a/f 1 b< 1.000 5.0< f DOE/ f< 200.0.