Abstract
A tunable-focus large aperture liquid lens is constructed using shape memory alloy (SMA) springs as actuators. The lens mainly consists of a shallow liquid-filled cylindrical cavity bound by a thin compressible annular rim and encapsulated by a flexible circular membrane on the top of the rim and a rigid circular plate at the rim bottom. The lens optical power is adjusted by a controlled compression of the annular rim via actuation of the three shape-memory alloy (SMA) springs. Since the volume of the cavity liquid is constant, the rim compression bulges the flexible membrane outward thus reducing its radius of curvature and the lens focal length. The fabricated tunable lens demonstrated an optical power range of 0-4 diopters utilizing a driving voltage less than 3V. Lens optical wavefront profiling was done using a Shack-Hartmann sensor displaying a RMS wave front error of 0.77 µm and 1.68 µm at 0 D and + 4 D. The aperture diameter and thickness of the fabricated lens are 34 mm and 9 mm, respectively, while weighing 16.7 g.
Highlights
A tunable focus lens, unlike a regular lens, is capable of adjusting focal lengths from a single lens structure according to external signals
The Alvarez lens consists of two plano-convex-concave lenses moving laterally against each other to change the focal length of the combined lenses [4]
In this paper we demonstrate the fabrication and testing of a compact tunable liquid lens actuated by low-weight shape memory alloy springs
Summary
A tunable focus lens, unlike a regular lens, is capable of adjusting focal lengths from a single lens structure according to external signals. Depending on the distance of lateral movement of its two lenses, it, loses the field of vision and suffers from a visible gap, imperfections, and friction in the sliding glass surfaces. Another adjustable focus lens mechanism has been implemented by utilizing graded indexchanging liquid crystals (LC) [5,6]. The lens consists of a reservoir bound by a rigid transparent circular plate at the bottom and a flexible membrane at the top In this lens, the fluid is stored behind the curved lens surface eliminating the need for external reservoirs. Fabrication and optical testing of these devices
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