Patent ID: 7692871
Filing Date: 2010-04-06
Classification: G02B

Abstract:
1. A zoom lens device comprising, from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power; and a fourth lens unit having a positive refractive power, wherein zooming is performed by changing distances between the lens units, wherein the first lens unit is moved towards the object side after being moved towards the image side during zooming from a wide-angle end to a telephoto end, so that the first lens unit is positioned closer to the object side at the telephoto end than at the wide-angle end, and wherein the following conditions are satisfied: where a distance between a position of the first lens unit at the wide-angle end and a position of the first lens unit that is maximally moved towards the image side is Ximg, a distance between the position of the first lens unit at the wide-angle end and a position of the first lens unit that is maximally moved towards the object side is Xobj, and a focal length of the zoom lens device at the wide-angle end is fw.