Patent ID: 6157496
Filing Date: 2000-12-05
Classification: G02B

Abstract:
A zoom lens system, comprising:a first positive lens element group located at a first position along an optical axis, the first lens element group having a first plurality of lens elements each having only spherical surfaces;a second negative lens element group moveable along the optical axis on an image side of the first lens element group, the second lens element group having a second plurality of lens elements consisting of three lens elements including a lens element having at least one aspherical surface located on an image side of the second lens element group;a third positive lens element group moveable along the optical axis on an image side of the second lens element group, the third lens element group providing a majority of the magnification change during a zooming operation and having a third plurality of lens elements including a pair of lens elements each having at least one aspherical surface; andan aperture stop positioned along the optical axis between the second lens element group and the third lens element group, the aperture stop remaining stationary during a wide angle-to-normal portion of a zooming operation and moving in unison with the third lens element group during a remainder portion of the zooming operation.