Remote acquisition of sound wave in transparent sound insulation screen by common-path digital holography

Aiming at the requirement of remote acquisition of sound wave in transparent sound insulation screen, a method using common-path digital holography (DH) is proposed. The expanded and collimated laser illuminates on the reflector near the sound source in the sound insulation screen. The reflected light is divided into two beams in the receiving optical path. One of them is the object light, and the other is the reference light which is filtered by a spatial low-pass filter to retain the zero-order light. Then, a hologram is formed by interference of reference and object light on the surface of image sensor. A high-speed camera is used to capture the time series of hologram. The captured holograms are processed to obtain the phase distribution of the reflected light field. The remote acquisition of sound wave in the sound insulation screen is realized by selecting the phase of a certain point in the phase distribution map to form a phase time series, which represents the sound wave emitted by the sound source. Due to the common-path system, the detecting results are not affected by the airflow disturbance and environmental noise in the propagation path of the probe light. At the same time, there is no optical path length matching problem between the reference and object light. The experimental system is built with a high-speed camera with speed of 4230fps to verify the proposed approach. The experimental results show that the sound wave in the transparent sound insulation screen at a distance of 10m is successfully obtained by