New variable focal liquid lens system using antagonistic-type SMA actuator

This paper presents a new variable focal liquid lens system that uses a SMA (shape memory alloy) actuator. Making a conventional variable focal liquid lens system small and light is difficult, due to the requirement of a large and heavy actuator, such as a pump or an electric motor, to distribute the liquid in the liquid lens. Plus, focal control is also difficult, due to a nonlinear focal variation in relation to a linear actuation. Thus, to solve these problems, a new actuation system is proposed for a liquid lens that uses a SMA wire and rotating piston mechanism, in which a cylindrical cam structure is adopted to create a linear relationship between the radius of the curvature of the lens and the displacement of the actuator. A winding and antagonistic-type SMA actuator is also designed to produce a large displacement and fast response time. Experiments using a prototype demonstrate the efficiency of the proposed system.