Wiener-filter-based compensation of a transmitter’s radiation pattern using synthetic transmit aperture acoustic imaging

Airborne acoustic imaging has the capability of obtaining distance information of an object in a scene, the capability of distinguishing objects from the background or a texture and it can also estimate the velocity of objects. However, the nonideal radiation pattern of a transmitter used for insonifying an imaging space can degrade imaging results. In this work, radiation patterns have been investigated, and a new approach to decrease the effect of a transmitter's radiation pattern in acoustic imaging is proposed. The novelty of our proposed method is that we used the measurement-based transmitter's radiation compensation. The compensation can be accomplished without knowing anything about the model and characteristics of the transmitter, the receiver and the medium. We compensated for the transmitter's radiation pattern and reconstructed acoustic images using the synthetic transmit aperture imaging technique. The compensation was based on the radiation pattern obtained from real measurements using a Wiener filter. The Wiener filter was used to compensate for the nonideal radiation pattern of the ultrasonic transmitter for both the phase and amplitude aspects simultaneously. To verify the proposed method, an indoor airborne acoustic imaging experiment was conducted using a two-dimensional (2D) receiver array and a 2D transmitter array. The results show an obvious improvement in the vertical angular resolution of the reconstructed three-dimensional images as well as a satisfactory horizontal angular resolution.