Patent ID: 6654180
Filing Date: 2003-11-25
Classification: G02B

Abstract:
A zoom lens formed of only three lens groups, in order from the object side, as follows:a first lens group of negative refractive power; a second lens group of positive refractive power; and a third lens group of positive refractive power; wherein the first lens group includes, in order from the object side, a negative meniscus lens component having its concave lens surface on the image side and a positive meniscus lens component having its convex surface on the object side, and the negative meniscus lens component includes a lens element having an aspherical lens surface; the second lens group includes, in order from the object side, a positive lens component with its lens surface of greatest curvature being convex and on the object side, and a negative lens component with its lens surface of greatest curvature being concave and on the image side, the second lens group includes a diaphragm for limiting light passing through the zoom lens, and the second lens group includes a lens element having an aspherical lens surface; all three lens groups move when zooming, and the second and third lens groups move toward the object side and decrease their distances from the first lens group during zooming from the wide-angle end to the telephoto end; the distance between the second and third lens groups remains substantially constant when zooming while the zoom lens is focused at infinity; the third lens group is moved toward the object side when focusing from infinity to a near point; and the following condition is satisfied: â€ƒ0.082W/f3<0.15â€ƒwhere D2W is the distance along the optical axis, when the zoom lens is at the wide-angle end and focused at infinity, between the lens surface of the second lens group that is nearest the image side and the lens surface of the third lens group that is nearest the object side; and f3 is the focal length of the third lens group.