Underwater acoustic imaging: An assessment of feasibility

Ideally, an ultrasonic imaging system operating in the reflective mode would construct a recognizable two-dimensional image of an object in the presence of various disturbances any of which, in the absence of adequate detail, could be erroneously identified as the object itself. The final output of any such imaging system may be considered as a two-dimensional array of independent information elements; the number of image elements, in general, equaling the total number of information channels. The elements may use a common carrier either in part or in the entirety on their respective transmission channels. In all cases there is a transmitter, an object to be visualized, an electro-acoustic receiving device, an amplifier system, and an electro-optical display. It is concluded that it does appear possible to design an imaging system which uses both the diffuse and specular components of the backscattered ultrasonic energy from a submerged object that will yield detail and shape information superior to that obtained by specular return alone. A reasonable range for a compact system appears to be about 30 meters. Two major physical limitations are: 1. The extremely low diffuse power reflected from the relatively smooth targets which are anticipated, and 2. The large specular-to-diffuse reflected power ratio which can result in 11blooming11 due to the finite aperture of the imaging system.