A new technology for focus variation with direct electric control without moving part will be presented. The technology relies on an interface between two non-miscible transparent liquids, which can be deformed by electrowetting. This technology has been developed since 10 years in the lab and starts to be available commercially, with the following characteristics: large amplitude of dioptric correction (20 dioptries for a 5mm pupil size), fast response, small power consumption and good transmission in the visible range, clear pupil 1-10mm diameter. This paper will show the basic principle, as well as the physical limitations and optical aberrations due to differential thermal expansion of the two liquids in the cell. Experimental measurements made with a Schack Hartmann wave front analyzer will be presented, as well as numerical simulations of the liquid-liquid interface. Applications will be discussed, mainly in consumer electronics.
We present real-time measurements of the wave front distortion induced by a variable focal lens. This lens, called Varioptic, is made of a transparent cell filled with twin liquids. We submit a 4.5mm in diameter lens upon a 110V voltage step inducing a optical power shift of about 25 dioptries (m-1) . Characteristic response time is shown to be of the order of a few 1/100s, the lens recovering its full quality after 5/100s. We present a scaling analysis of this response time versus lens size.