Optical feedback interferometry applied to visualize an acoustic stationary wave

This article presents a novel technique to acquire and visualize two-dimensional images of dynamic changes of acoustic pressure in the case of a stationary acoustic wave. This method uses optical feedback interferometry sensing with a near-infrared laser diode. The stationary acoustic wave is generated using two piezoelectric transducers of 40 kHz facing each other, dynamic changes in acoustic pressure are measured in a 100 mm x 100 mm acoustic propagation field whose refractive index is variable along the optical path of the laser from the laser diode to a distant mirror and vice-versa. The image system records an image of 100 x 100 pixels of the acoustic pressure variation.