Patent ID: 6351337
Filing Date: 2002-02-26
Classification: G02B

Abstract:
A zoom lens formed of only three lens groups, in sequential order from the object side, as follows:a first lens group of negative refractive power, said first lens group consisting of two lens elements of negative and positive refractive power, respectively, in order from the object side, at least one of said two lens elements including a surface that is aspherical; a second lens group of positive refractive power and that includes a stop, said second lens group including a surface that is aspherical; and a third lens group of positive refractive power, wherein when zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group decreases and both the second and the third lens groups move toward the object side; when changing the focus from an object at an infinite distance to a nearby object the position of the third lens group is shifted; and when focused on an object at infinity, the distance between the second lens group and the third lens group is kept substantially constant when zooming from the wide-angle end to the telephoto end.