Patent ID: 7502172

Claim:
A zoom optical system comprising, in order from an object side: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and a third lens unit having a positive refractive power, the zoom optical system changing a space between the lens units to thereby perform zooming and focusing, the first lens unit comprising a biconcave negative lens, the zoom optical system satisfying the following condition (1): −3.0<( r 1GF +r 1GR )/( r 1GF −r 1GR )<0.3 (1), wherein r 1GF denotes a paraxial radius of curvature of an object-side surface of the negative lens of the first lens unit, and r 1GR denotes a paraxial radius of curvature of an image-side surface of the negative lens of the first lens unit, and wherein the negative lens of the first lens unit has an aspherical surface whose negative refractive power weakens with distance from an optical axis.