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Fast focusing using a pinned-contact oscillating liquid lens

Abstract

Liquid lenses are attractive for applications in adaptive optics requiring a fast response1,2. In conventional designs focusing time is limited by liquid inertia and the time it takes for transients in lens shape to subside. As a result, operation is confined to after the oscillations have dampened3,4,5. Here we demonstrate a harmonically driven liquid lens with an oscillating focal length, which can capture any image plane in a given range by grabbing the image ‘in sync’ with the oscillations6. By oscillating the lens, the task of changing the focal length is effectively transformed from a mechanical manipulation to the electronic timing of image capture, which can be achieved much more quickly. High-fidelity imaging is demonstrated at 100 Hz for a millimetre-scale liquid lens, which is driven at resonance and features pinned contact lines. Theoretical predictions show that a significantly faster response is possible with scaled-down lenses.

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Figure 1: Time series of a pinned-contact oscillating liquid lens driven by an external pressure at resonance but with different forcing amplitudes.
Figure 2: Frequency response of liquid lenses.
Figure 3: Predicted and measured motion of the lens along with its respective focal length.
Figure 4: Focusing of a pinned-contact oscillating liquid lens as a function of time.
Figure 5: Frequency response of the pinned-contact oscillating liquid lens.

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Acknowledgements

The authors thank I. Martinovic for assisting with some of the experiments, P.H. Steen and M.J. Vogel for useful discussions, and H.A. Scarton for lending the precision microphone equipment and his expertise in calibrating the pressure transducers. This work was supported by National Sciences Foundation grant DMII-0500408.

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Correspondence to Amir H. Hirsa.

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López, C., Hirsa, A. Fast focusing using a pinned-contact oscillating liquid lens. Nature Photon 2, 610–613 (2008). https://doi.org/10.1038/nphoton.2008.198

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