Photoacoustic sonar: principles of operation, imaging, and signal-to-noise analysis in time and frequency domains

Abstract

A photoacoustic (PA) imaging methodology utilizing coded optical excitation and correlation signal processing has been described. The basic principles of using relatively long coded waveforms and a matched filter signal compression to increase signal-to-noise ratio (SNR) and axial resolution are common in conventional radar and sonar systems. To emphasize these similarities, the proposed technique is called the photoacoustic sonar (or radar). We describe the implementation of the PA sonar using a near-IR intensity modulated continuous wave laser source and frequency-domain correlation processing of the acoustic response. Application of the PA sonar for imaging of biological materials with discrete chromophores was studied using tissue mimicking phantoms. The SNR gain achieved with linear chirps is analyzed and compared with conventional time-domain photoacoustics.