Design and testing of a three-dimensional acoustical imaging system

The Acoustical Imaging Group of the Marine Physical Laboratory, Scripps Institution of Oceanography, is developing a real time, high resolution three-dimensional acoustical imaging system for use in the ocean. The system, called Fish TV (FTV) is designed for the observation of macrozooplankton and small fish. The system makes use of a set of eight transmitted fan beams and a set of eight receive beams rotated 90° with respect to the transmit beams. The resulting transmit/receive pairs form a set of 64 2° by 2° beams for an overall ensonified area of 16° by 16°. The third dimension, range, is provided by time. The system operates at a center frequency of 330 kHz, with a bandwidth of 30 kHz. An experiment using an artificial target, a 40 μsec long transmitted pulse, and minimal data processing indicates that the system tracks targets with accuracy