Cushman, Darby & Cushman
Vari-focal photographic lens system of rear lens group exchange type
 A vari-focal photographic lens system of rear lens group exchange type comprising a front lens group and a rear lens group and arranged to vary the focal length of the lens system as a whole by exchanging the rear lens group for another rear lens group having a different lens configuration, the vari-focal photographic lens system being arranged so compactly and arranged that the variation of aberrations is small. 
Olympus Optical Co., Ltd.
G
G02B
inventional
Hiroshi Masaki Toru
Takase Imaizumi Fujii