Abstract
A technique to create aspheric surface shapes on commercially available electrowetting liquid lenses is demonstrated. Based on a previously published surface oscillation model a technique using a Hankel transform is proposed and tested experimentally. An alternating actuation voltage is applied to the liquid lens to stimulate surface oscillations, that temporarily add up to the desired surface shape. The voltage signal can be repeated at video rate. The measurements were taken with a Mach-Zehnder interferometer and confirm the previous results. The capabilities and limitations of the proposed method are demonstrated using the examples of a Bessel surface, spherical aberration, an axicon, and a top hat structure.
Highlights
The performance of electrowetting liquid lenses is limited by surface oscillations
As an alternative approach we focused on studying the nature of surface waves on a commercially available liquid lens and its resonance modes in order to avoid, or even to make use of them.[11]
The presence of Bessel shaped modes as predicted by the previously published analytical model can be confirmed with the interferometric surface measurement
Summary
Already when the first liquid lenses (LL) were developed, it became clear, when switching the focal distance too fast, the liquids inertia prevents the liquid surface from following the change instantaneously.[1,2] Surface waves are created. These uncontrolled deviations from a spherical interface were identified as the cause of dynamic aberrations and have limited the operational speed of liquid lenses. In this paper we will confirm the results of our previously published model with a second interferometric approach and investigate to what extend it is possible to create aspheric shapes on the liquid lens
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