A Statistical Method for Autofocus of Synthetic Aperture Sonar Images

In this paper we present preliminary results of a new technique for autofocus of synthetic aperture sonar (SAS) imagery, which employs global optimisation techniques based on image quality measures and motion statistics of the towfish. From each reconstructed image a quality measure is calculated and balanced with a cost measure calculated from the known statistics of the towfish motion. This is used to perturb the estimated towfish path and a new image is reconstructed. Using only a simple image contrast measure the preliminary results seem promising although the technique is very computationally expensive. It is envisaged that the technique could be improved by the choice of better image quality measures.