Photographic optical system and image pickup apparatus including the photographic optical system

An image pickup apparatus comprising:

• a photographic optical system;
• and
• an image sensor or a film surface configured to receive an image formed by the photographic optical system,
• the 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, d1ab is an air space between the first lens sub-unit and the second lens sub-unit, f1a is a focal length of the first lens sub-unit, f1b 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<d1ab/(L×Fno)<0.2000
• -1.000<f1a/f1b<1.000
• 5.0<fDOE/f<200.0.