Opt. Express 21, 8669–8676 (2013)

Compact, adaptive lenses with adjustable focal lengths are particularly attractive for space-constrained applications such as endoscopes, cellular phone cameras, web cams and machine vision systems. Now, Samuel Shian and colleagues from Harvard University in the USA report a simple, self-contained adaptive lens whose focal length can be varied through an integrated electrical actuator lying in the optical path of the lens. The lens consists of a stiff frame and a clear liquid housed between two membranes, one passive and the other electroactive. The latter is made from a transparent dielectric elastomer coated on both sides with transparent flexible electrodes. The focal length of the lens is varied by altering the relative curvatures of the two membranes. This is done by applying a voltage to the active membrane, causing it to deform and hence changing the liquid pressure, which, in turn, alters the curvature of the passive membrane. The researchers report a change in focal length of over 100% with a response time of less than 1 s. Numerical analysis indicates that appropriate selection of the lens geometry should give even better performance.