Plenoptic cameras generally employ a microlens array positioned between the main lens and the image sensor to capture the three-dimensional target radiation in the visible range. Because the focal length of common refractive or diffractive microlenses is fixed, the depth of field (DOF) is limited so as to restrict their imaging capability. In this paper, we propose a new plenoptic camera using a liquid crystal microlens array (LCMLA) with electrically tunable focal length. The developed LCMLA is fabricated by traditional photolithography and standard microelectronic techniques, and then, its focusing performance is experimentally presented. The fabricated LCMLA is directly integrated with an image sensor to construct a prototyped LCMLA-based plenoptic camera for acquiring raw radiation of targets. Our experiments demonstrate that the focused region of the LCMLA-based plenoptic camera can be shifted efficiently through electrically tuning the LCMLA used, which is equivalent to the extension of the DOF.
A focus-swing liquid-crystal (LC) microlens with two patterned electrodes and filled in nematic liquid crystal is proposed. In order to lower the level of the applied voltage signal and effectively increase the focus-swing range, the bottom electrode is designed as a circular patterned structure. The top electrode is composed of four stripe-patterned subelectrodes, which are powered, respectively to generate expecting potential and drive the focus swing in the focal plane of the microlens. The common optical properties of the LC microlens and the swing behavior of the formed focus in the focal plane are demonstrated experimentally.
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