Compact, high-speed variable-focus liquid lens using acoustic radiation force

A compact, high-speed variable-focus liquid lens using acoustic radiation force is proposed. The lens consists of an annular piezoelectric ultrasound transducer and an aluminum cell (height: 3 mm; diameter: 6 mm) filled with degassed water and silicone oil. The profile of the oil-water interface can be rapidly varied by applying acoustic radiation force from the transducer, allowing the liquid lens to be operated as a variable-focus lens. A theoretical model based on a spring-mass-dashpot model is proposed for the vibration of the lens. The sound pressure distribution in the lens was calculated by finite element analysis and it suggests that an acoustic standing wave is generated in the lens. The fastest response time of 6.7 ms was obtained with silicone oil with a kinematic viscosity of 100 cSt.