Actuator enables fast focusing of liquid lens

Researchers Hiromasa Oku and Masatoshi Ishikawa at the University of Tokyo (www.u-tokyo.ac.jp) have developed a rapidly deformable, variable focus liquid lens in which they can change and control shape within a few milliseconds using a stack of piezoelectric actuators.

Two immiscible liquids are located in two chambers connected via a circular hole. A liquid-liquid interface is formed at the hole, which works as an aperture of the lens. This interface works as a refractive surface because of the different refractive indices of the two liquids. The lower chamber is equipped with a deformable wall that the actuator pushes to change the chamber’s volume and the interface curvature.

The prototype has achieved a 2-ms step response time and a minimum rms wavefront error of only 80.3 nm. The researchers expect this device to be useful for axial focus scanning for microscopes, focusing and zooming for camera lenses and machine-vision systems, and beam-focus control in both laser machining and laser trapping. For a paper published by SPIE and videos, visit http://spie.org/x38198.xml?highlight=x2422&ArticleID=x38198.