Three-dimensional ultrasonic sensing of underwater animals

A three-dimensional sonar imaging system whose goal is to track small animals in the water column is under development. The system uses an array of stacked transmit (8) and receive (8) transducers operating at 430 kHz. This permits an 8-beam by 8-beam view of a 16° by 16° wedge at frame rates of 1 frame/s to a range of approximately 10 m. Over this field of view, the system produces calibrated target strengths of the objects that are being imaged. Data from test targets and small fish in a test tank have been used to create animated films of rendered three-dimensional images. These preliminary data indicate that 3-D ultrasonic imaging is a viable technique for tracking small animals