Patent ID: 7268811
Filing Date: 2007-09-11
Classification: G02B

Abstract:
1. A zoom lens system comprising, in order from an object side to an image side: a first lens unit of positive optical power, the first lens unit consisting of one positive lens element and one negative lens element in order from the object side to the image side; a second lens unit of negative optical power, the second lens unit consisting of two negative lens elements and one positive lens element; a third lens unit of positive optical power, the third lens unit consisting of one positive lens element and one negative lens element; and a fourth lens unit of positive optical power, the fourth lens unit comprising one positive lens element and one negative lens element, wherein at least the first, third and fourth lens units move during zooming so that the distance between the first lens unit and second lens unit increases, the distance between the second lens unit and third lens unit decreases and the distance between the third lens unit and fourth lens unit decreases at a telephoto end compared to a wide-angle end, at least one aspherical surface is provided on the fourth lens unit or a lens unit on the image side thereof, and the zoom lens satisfies the following conditions: where fi represents a focal length of an i-th lens unit and fw represents a focal length of the entire system at the wide-angle end.