Cushman, Darby & Cushman
Compact vari-focal photographic lens system
 A compact vari-focal photographic lens system comprising a master lens system and an auxiliary lens group wherein the master lens system comprises a front lens unit having positive refractive power and a rear lens unit having negative refractive power, the compact vari-focal photographic lens system being arranged to vary the focal length of the lens system as a whole by inserting and removing the auxiliary lens group to and from the image side of the master lens system and arranged that the overall length of the lens system is short, it is possible to vary the focal length without moving the stop mechanism, and aberrations are corrected satisfactorily favorably, the compact vari-focal photographic lens system being suitable for the use with popular cameras. 
Olympus Optical Co., Ltd.
G
G02B
inventional
Masaki Toru Hiroshi
Imaizumi Fujii Takase