Design of a twenty-element long focal length zoom lens

An optical lens system with varying magnification has been designed for a 70-mm image format. Twenty optical elements were needed to provide for the 345- to 1050-mm focal length zoom range as well as the proper color correction over the visible spectrum. A 4-in diameter port window limits thef/# of the optical lens system. Operation of the lens system is done by actuating stepping motors through a MacPlus computer. This lens system was designed for Los Alamos National Laboratory Group M-8, because no commercial zoom lens existed that would change its reduction from 1/15 to 1/4 at a focusing range of 5 meters. Additionally, we required a larger, non-standard image size that could be recorded by a rotating mirror streak camera. A Nikkor lens sales manual does offer a long focal length, 35-nun lens only upon special order. The closest focusing range of this Nikkor lens is 6 meters.