Vario-objective system of negative positive and negative lens groups changes focal length by adjusting lens grooves along optical axis with specified focal length amd magnification conditions.

摘要

The vario-objective system includes first negative, second positive and third negative lens groups as viewed from objective, changing focal length by shifting first to third groups respectively along the optical axis. In this (lf1/f21) is between 1.3 and 1.8. Again (f3/fw) is between 2.0 and 3.4 and (m3t/m3w) lies between 1.05 and 1.25. In this (fw) denotes the focal length of the vario-objective system in the short limit position, (f1) the focal length of the first lens group, (f2) the second group and (f3) the third group respectively. (m3w) is the magnification of the third lens group in the short limit position when focusing on an infinitely distant object and (m3t) is the magnification of the third lens group in the long limit focal length setting.