Liquid lens based on electromagnetic actuation for high-performance miniature cameras

This paper presents a new design of tunable liquid lens operated by electromagnetic actuation for autofocus (AF) in miniature cameras and its optical performance is experimentally verified. When an electrical voltage is applied to an electric coil inside the electromagnetic system beneath the liquid lens, a magnetic field is generated around the electromagnetic system based on Faraday's law of induction. The magnetic field is used to actuate a ring type neodymium magnet placed on the top of an elastic membrane in the liquid lens. Based on the proposed liquid lens, the measurement of the lens sag height with respect to an applied voltage is carried out. The lens sag height is linearly increased from -1 mm to 0.8 mm while the applied voltage is changed from 0 V to 50 V at a 5 V increment. The average sag height variation per voltage is about 32 μm. The focal length with respect to an applied voltage is also measured using a custom-built testing system consisting of a laser, a mirror, a liquid lens and a detection screen and compared with theory. Finally, the ability of the liquid lens to change its focal plane to distinguish two objects positioned at different distances is successfully tested.