Patent ID: 6611386
Filing Date: 2003-08-26
Classification: G02B

Abstract:
A three-group zoom lens comprising, in the order from the object side:a first lens group having negative refractive power which consists of a negative lens element nearest the object side and a positive lens element nearest the image side; second lens group having positive refractive power that includes, in order from the object side, a stop for controlling the brightness of an image, two positive lens elements, and a negative lens element; and a third lens group having positive refractive power; wherein each of the first, second and third lens groups includes at least one aspherical surface; when zooming from the wide-angle end to the telephoto end, the first lens group is moved nearer the second lens group, and the second and third lens groups are each moved toward the object side; when focusing from an object at infinity to a nearby object, the third lens group is moved toward the object side; the third lens group includes a positive meniscus lens element having surfaces of different radii of curvature, with the surface of smaller radius of curvature being convex and on the object side; and the negative lens element in the first lens group and at least one of the positive lens elements in the second lens group each include an aspherical surface.