State of the art in underwater acoustic imaging

Underwater acoustic imaging is a part of the larger field of acoustic imaging, and as such, has its own peculiarities and attributes as compared with the rest of the acoustic imaging field. Such systems are useful in providing underwater observation and inspection capabilities whenever optical systems cannot. Three basic techniques of acoustic imaging that are appropriate for underwater imaging use (focused, beamformed, and holographic) and examples of each of them are described. Then the limitations and promise for the future in underwater acoustic imaging is explored.