VARIABLE MAGNIFICATION OPTICAL SYSTEM IN FINITE CONJUGATE LENGTH

摘要

PURPOSE:To make an optical system small-sized and improve the capacity and extend the magnification range by constituting the optical system with four lens groups and arranging fixed lens groups having a negative refracting power and moving lens groups, each of which consists of positive, negative, and positive lenses, symmetrically with respect to a stop respectively. CONSTITUTION:The optical system consists of the first fixed lens I having a negative refracting power, the second moving lens group II consisting of positive, negative, and positive lenses and having a positive refracting power, a stop 5, the third moving lens group III symmetrical to the lens group II with respect to the stop, and the fourth fixed lens symmetrical to the first lens I with respect to the stop which are arranged in order from the incident light side. Individual groups are placed symmetrically in case of unmagnification, and they are placed asymmetrically and are moved in the direction of the optical axis as one body in case of variable magnification. Thus, the projection magnification is varied while keeping the distance between an object and the image constant.