Zoom lens of the telephoto type having four lens groups with rear-focusing

摘要

A zoom lens includes, from the object- to image-side, a positive first lens-group (G1), a negative second lens-group (G2), a positive third lens-group (G3) and a positive rear lens-group (R). During zooming from the wide-angle to the telephoto end, the interval between the first (G1) and the second lens-group (G2) increases and the interval between the second (G2) and the third lens-group (G3) decreases. The rear lens-group (R) includes a positive first sub-group (Ra), a negative second sub-group (Rb) and a positive third sub-group (Rc). Close focusing is performed by moving the second sub-group (Rb) towards the image side. The zoom lens also satisfies the following iequalities: 0.2 < frt/ft < 1.8 (1) and 0.2 < | fb | / frt < 1.0 (2), where "frt" denotes the focal length of the rear lens-group (R) at the telephoto end, "fb" denotes the focal length of the second sub-group (Rb) and "ft" denotes the focal length of the whole zoom lens at the telephoto end.