Tubular Focus-Tunable Fluidic Lens Based on Structured Polyimide Foils

We demonstrate an entirely new means for fabrication of focus-tunable fluidic lenses using a tubular geometry with great design flexibility. The technology is based on patterned, flexible polymeric foils inserted into a cylindrical tube, which is filled with two liquids of different refractive indices. Electrowetting is used for actuation of the liquid/liquid interface, thus realizing focus tunability. To show the utility of this approach, a single liquid lens with a 4.5-mm aperture and of a back focal length tuning by a factor of 7, requiring actuation voltages below 100
$\text{V}_{\mathrm{ rms}}$
, is demonstrated. The tubular geometry optical resulted in a high optical surface quality over the entire actuation range, with rms values for wavefront error below
$\pmb {\lambda }/2$
, is dominated by spherical aberration.