Patent ID: 7236305

Claim:
A zoom lens comprising the following elements arranged in the mentioned order from an object side to an image side: a focusing lens unit; a variator lens unit that moves along an optical axis during zooming; a compensator lens unit that moves along the optical axis to compensate image plane variation during zooming; an aperture stop for regulating light quantity; and a relay lens unit that is kept stationary during zooming, wherein the relay lens unit includes a lens unit L 21 including a branch element, a lens unit L 22 that is interchangeable with an extender lens unit L 22 ex that can be inserted into or removed from the optical path to change focal length range of the entire lens system and a lens unit L 23 having a positive refractive power, arranged in the mentioned order from the object side to the image side, and wherein the zoom lens satisfies the following conditions:  e 22 e 20 + e 21  < 1.5  ϕ 21 ϕ w  < 0.6 where e 20 represents a distance from the aperture stop to a position of a front side principal point of the lens unit L 21 , e 21 represents a distance from a position of a rear side principal point of the lens unit L 21 to a position of a front side principal point of the lens unit L 22 , e 22 represents a distance from a position of a rear side principal point of the lens unit L 22 to a position of a front side principal point of the lens unit L 23 , Φ 21 represents a refractive power of the lens unit L 21 , and Φ W represents a refractive power of the entire system of the zoom lens at the wide-angle end.