Ultrasonic optical lens array with variable focal length and pitch.

An optical lens array whose focal length and lens pitch can be varied by acoustic radiation force was investigated. It has no mechanical moving parts and a simple structure that consists of a glass plate, four ultrasound transducers, and a viscoelastic film. A lens array can be formed by generating acoustic radiation force through flexural vibrations of the glass plate. Its focal length can be controlled by varying the voltage applied to the transducers and the lens pitch can be altered by changing the driving frequency.