Cushman, Darby & Cushman
Compact zoom lens system having three lens groups
 A compact zoom lens system having excellent performance and comprising a first lens group having positive refractive power, a second lens group having negative refractive power and a third lens group having positive refractive power, said third lens group being fixed relative to the image plane, said second lens group being moved along the optical axis for varying magnification, and deviation of the image position caused by moving said second lens group is compensated by moving said first lens group. 
Olympus Optical Co., Ltd.
G
G02B
inventional
Tooru
Fujii