US Patent 7227698 Optical unit, and image taking apparatus provided therewith

A plurality of lens units in an optical unit has at least: from the object side toward the image side, a first lens unit having a positive optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power. When at least the first lens unit moves from the image side to the object side in zooming from the wide-angle end position to the telephoto end position, at least one gap between the lens units varies. Predetermined conditional formulae are satisfied.