Cushman, Darby & Cushman
Zoom lens system
 A zoom lens system comprising a first, second, third and fourth lens groups, the first lens group being a focusing lens group and having positive refractive power, the second lens group being a variator and having negative refractive power, the third lens group being a compensator and having positive refractive power, the first, second and third lens groups constituting a varifocal subsystem, the fourth lens group being a relay lens, which comprises a first lens component comprising a positive lens and a negative lens and having positive refractive power as a whole, a second lens component comprising a positive lens, a third lens component comprising a negative lens, and a fourth lens component comprising a positive lens, the zoom lens system being small in size, light in weight and arranged that aberrations are corrected favourably. 
Olympus Optical Co., Ltd.
G
G02B
inventional
Kazuo Tooru
Ikari Fujii