Patent ID: 7145735

Claim:
An image pickup optical system, in order from an object side to an image side, comprising: a first lens unit with positive optical power, the first lens unit having a first lens sub-unit and a second lens sub-unit in order from an object to an image side; a second lens unit with negative optical power; a third lens unit with positive optical power; and a fourth lens unit, wherein the second lens unit moves toward an image side and the third lens unit moves toward an object side respectively during focusing from an infinite object to a short distance object; wherein the second lens sub-unit displaces an image formed by the image pickup optical system in a direction orthogonal to an optical axis, by moving so as to have a component in a direction orthogonal to the optical axis; and wherein the following condition is satisfied: 0.8 <|Δx/ΔH|< 1.5 where “ΔH” represents a movement amount of the second lens sub-unit in a direction orthogonal to the optical axis, and “Δx” represents a displacement amount of an image formed by the image pickup optical system in the direction orthogonal to the optical axis with respect to the movement amount ΔH of the second lens sub-unit.