Three-dimensional focus scanning by an acoustic variable-focus optical liquid lens

This paper describes a liquid lens whose focal point can be varied in both the axial and radial directions by acoustic radiation force. The liquid lens consists of a lens cell, two immiscible liquids with different refractive index (water and silicone oil), and an annular PZT transducer with four-divided electrodes. The oil-water interface acting as the lens surface can be deformed by the acoustic radiation force, and the focal point can changed three-dimensionally and the lens acts as a variable-focus lens. The displacement angle in the radial direction was approximately 3 degrees when the input voltage was 45 V at 1.9 MHz. By exciting with AM signals, the hemispherical water droplet oscillated and the focus scanning in the axial and radial directions could be achieved.