Cushman, Darby & Cushman
Zoom lens system
 A zoom lens system with a zoom ratio about 3 comprising a first lens group to be used for focusing, a second lens group which is a variator, a third lens group which is a compensator, and a fourth lens group which is a master lens, the second lens group being provided with a lens surface having the correcting function for chromatic aberration and a lens surface having the correcting function for spherical aberration so that chromatic aberration of spherical aberration is thereby corrected favorably. 
Olympus Optical Co., Ltd.
G
G02B
inventional
Tooru
Fujii