A simple and low-cost solution to reduce the height and weight of extended hemispherical lenses is proposed based on the introduction of a cylindrical air cavity above the primary feed. The presence of an additional air-dielectric interface enables one to shorten the focal length of the lens, which leads to antenna height and weight reductions of 13% and 27%, respectively. The communication describes the design principle and performance characteristics of the reduced-size integrated lens antenna, superimposed with a conventional synthesized elliptical one. Both prototypes are fabricated in Rexolite and measured in Ka band. A good agreement between the performance characteristics of the antennas is observed. The additional advantages of the proposed approach are explained, and its applicability for lens antennas made of high-k materials is discussed.