The purpose of this research is to create a real-time, three- dimensional ultrasonic imaging device that can be used by an underwater robot. It will employ techniques combining spread spectrum systems and sparse arrays. First, a device will be constructed to measure the coherence time for the underwater channel and for use as a general purpose imaging system. Then, the results of the coherence measurements will be incorporated into the design of the spread spectrum signals. The result of the signal design will be tested via computer simulation and physical measurement. Subsequent investigations will include refinements on signal coding, spatial coding techniques, and the performance limitations inherent in such an ultrasonic device. A successful development under this grant will help to advance the state of the art of vision sensors useful for robots in vision-impaired environments, particularly underwater.
