State-of-the-art tools for next-generation underwater optical imaging systems

The detection and identification of underwater threats in coastal areas is of interest to the Navy. Conventional optical imaging systems are limited to scenarios where the number of attenuation lengths between the system and the object are less than 4. With a desire to operate at extended ranges and threats becoming smaller and better camouflaged, new approaches are needed. In response to these challenges, new transmitters and receivers are being developed to support the next-generation of underwater optical imaging systems. One of these systems is based on the modulated pulse concept where a pulsed laser source is encoded with a radar signal, and a range-gated, high-speed optical receiver recovers the radar modulation envelope. Subsequent processing of the radar signal provides a way to discriminate against multiply scattered light and to enhance image contrast and resolution. The challenge is developing transmitter and receiver hardware that meets the requirements of the modulated pulse technique. We report recent progress that has been made in developing modulated pulse transmitter and receiver hardware. A working prototype was demonstrated and tested in a controlled laboratory environment. The results of these initial experiments are presented.