A Liquid Lens Driven by Bubble Actuator

Abstract

We report an adaptive-focus lens using two immiscible liquids. The two liquids have a spherical interface and their border is confined by an iris diaphragm (ID). Using a bubble actuator to vary the aperture of the ID, the surface profile of the two liquid is changed, which in turn leads to a tunable focal length. In this paper, the liquid lens structure is depicted and the operation mechanism of the bubble actuator is introduced. For the liquid lens, the refractive index (n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ) of the convex liquid is smaller than that of the concave (or surrounded) liquid (n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ~ 0.2), so the lens is a diverging lens. As the aperture of the diaphragm is changed from ~ 5 to ~ 7.5 mm by the actuator, the focal length (f) of the lens could be tuned in the range of -168 mm ≤ f ≤ -55 mm. For the bubble actuator, it has the advantages of voltage control, large actuation pressure, reasonable speed, and low power consumption. Driven by the bubble actuator, our liquid lens can present a large aperture change, reasonable dynamic response, and precise focus control.