Variable lens system with a high focal length ratio for a photo camera has two negative and two positive lens groups each movable along the optical axis

摘要

The variable lens system has a positive first (10) lens group, a negative second lens group (20), a positive third lens group (30) and a negative fourth lens group (40) positioned in this order from the object. The four lens groups are each movable along the optical axis for altering the focal length.