| 摘要 |
PURPOSE:To make a large-aperture zoom lens compact and, at the same time, to minimize the variation of the spherical aberration and coma aberration, by constituting the zoom lens of a variable power system composed of the 1st group of a focusing element, 2nd group of a variator element, and 3rd group of compensator element, and a relay system. CONSTITUTION:A variable power system is constituted by successively arranging from the object side the 1st group I of a focusing element which has a positive focal length and does not move at the time of variable power, but is movable at the time of focusing only, the 2nd group II of a variator element which has a negative focal length, is movable at the time of variable power only, and principally has a variable power function, and 3rd group III of a compensator element which has a negative focal length, is movable, and principally corrects the focusing position at the time of variable power. Moreover, the 4th group IV is arranged as a relay system. The 4th group IV is composed of a front element IVa comprising at least a positive lens, another positive lens with the strongly convex surface facing the object side, and negative lens with the strongly concaved surface facing the object side, and a rear element IVb comprising a negative lens and at least two positive lenses. |
