Zoomar lens
The Zoomar lens was the first commercially successful zoom lens, designed by optical engineer Frank G. Back as an outgrowth of his research on viewfinders and variable focal length projectors for the United States military. == History == Back developed an accessory "Vario-focus" viewfinder (designated PH-532/UF) for the Bell & Howell Eyemo camera variant PH-330-C issued by the United States Army Signal Corps during World War II; this incorporated many of the same principles as the commercial Zoomar lens, including the use of optical compensation.