Patent ID: 8873158
Filing Date: 2014-10-28
Classification: G02B

Abstract:
1. A zoom lens comprising, in order from an object side to an image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power, wherein at a time of zooming from the wide angle end to the telephoto end, the lens units move in such a way that the distance between the first lens unit and the second lens unit decreases and the distance between the second lens unit and the third lens unit increases, and the zoom lens satisfies the following conditions: where ft is the focal length of the entire system at the telephoto end, f1 is the focal length of the first lens unit, Npa is the average of the refractive indices of the materials of all the positive lenses in the entire system, fpa is the average of the focal lengths of all the positive lenses in the entire system, and fw is the focal length of the entire system at the wide angle end, and νna is the average of the Abbe constants of the materials of all the negative lenses in the entire system.