| 摘要 |
PURPOSE:To make a zoom lens compact, by fixing the first lens group having a positive refracting power and moving the second lens group having a positive refracting power and allowing extents of movement of two lenses of the second group to satisfy a specific conditional expression in case of zooming. CONSTITUTION:In case of zooming, the fixed first lens group having a positive refracting power and the second lens group which is arranged at the rear of the first lens group and has a positive refracting power are moved toward an object and are focused to the close-distance object. At this time, the direction of extension from an infinity object to the closest-distance object is always constant during zooming and is the direction toward the object and is not discontinuous halfway. Though the quantity of extension of the second lens group is increased according as zooming to the telephoto side, the quantity of extension is reduced considerably because the focusing interval is increased, and thus, the zoom lens is made compact. If an expression is satisfied when extents of movement of two lenses of the second group are denoted as (s) and (t) respectively, the zoom lens is made compact also. |
