Development of Miniature Tunable Multi-Element Alvarez Lenses

The design, fabrication, and characterization of miniature tunable multi-element Alvarez lenses are reported in this paper. Optical design including optimal lens configuration and surface coefficient selection, together with the effects of assembly errors on lens performances, is numerically studied using the ray-tracing method. To demonstrate the working principle, a four-element Alvarez lens is experimentally demonstrated in comparison with a conventional two-element lens. Lens elements are fabricated by a diamond turning and replication molding process and are driven by two piezo actuators integrated with displacement amplification mechanisms. Dynamic tuning of optical power is experimentally determined to be around 43.2 diopters (from 50.9 to 94.1 diopters) for the four-element lens and 21.1 diopters (from 25.3 to 46.4 diopters) for the two-element lens. Lens imaging performance is also characterized comparatively, indicated by images of the 1951 USAF resolution test chart through the lens and Modulation Transfer Function curves calculated accordingly.