Focussed or lens-type ultrasonic imaging for small deep- diving submersibles

This paper summarizes the results of an investigation into the critical problems of developing a practical focussed or lens-type ultrasonic image converter for small submersibles capable of operating to 20,000-foot depths. The problems of specular reflections, lens depth of field, and acoustic absorption are described. Trade offs between information rate, complexity, and imaging performance are discussed. A simple, partially filled rotating array converter is proposed as the most cost effective approach for an operational system using current technology. Results from high-pressure tests of experimental array elements are presented.