Movable optical lens array using acoustic radiation force

A movable optical lens array that utilizes acoustic radiation force was investigated. The lens array consists of a rectangular glass plate, two piezoelectric bimorph transducers, and a transparent viscoelastic gel film. By electrically exciting the transducers, the flexural vibration mode was generated along the glass plate. The acoustic radiation force acts to the surface of the gel so that the surface profile can be deformed and the lens array can be fabricated. A cylindrical lens array with the lens pitch of 4.6 mm was fabricated at 113 kHz. The lens positions correspond with the loop positions of the flexural standing wave, and the lens pitch corresponds with half the wavelength of the flexural vibration of the glass plate. The focal points of the lens could be changed by the input voltage, and the lens can act as a variable-focus lens. The lens positions could be moved in the length direction by two-phase drive. The moving distance of the lens was 4.6 mm when the driving phase difference between the two transducers changed from 0 to 360°. The translation of the lens array was applied as an optical scanner.