HIGH VARIABLE POWER RATE ZOOM LENS WITH SMALL SHORT-DISTANCE ABERRATION VARIATION

摘要

PURPOSE:To obtain excellent performance from infinity to a short distance by stabilizing the performance of a three-group zoom lens and a four-group zoom lens in short-distance focusing. CONSTITUTION:The zoom lens consists of a 1st positive lens group I, a 2nd positive lens group II, and a 3rd negative lens group III and the power is varied from a wide-angle end to a telephoto end by moving the respective lens groups toward an object. While the most image-side lens element LF among lens elements constituting the 2nd lens group is fixed at a constant position, the remaining lens elements of the 2nd lens group are moved toward the object and the lens system consists of the 1st positive lens group I, the 2nd positive or negative lens group II, the 3rd negative lens group III, and a 4th negative lens group IV; and the power is varied from the wide-angle end to the telephoto end by moving the respective lens groups along the optical axis respectively. The most image-side lens element LF among elements constituting the 3rd lens group is fixed at a constant position and the remaining lens elements of the 2nd and 3rd lens groups are moved toward the object to put the lens system in focus.