Extended Range Optical Underwater Imaging

The Navy needs a compact extended range underwater imaging system that can image through > 6 attenuation lengths with 0.25" resolution. Present systems are limited by scattering to ~ 5 attenuation lengths. To meet the need, we propose a compact, adaptive raster scanner, using a doubled Yb fiber laser for the transmitter, a wide field-of-view (FOV) receiver, and an annular APD detector array, enabling adaptive data processing. The fiber laser offers excellent packaging, robustness, and output characteristics for improved S/N. The receiver offers improved collection efficiency, and the annular array adaptively balances S/N and resolution needs. The proposed system is estimated to have two decades more dynamic range than current imaging systems. Phase I is a design study on the proposed system. Optical design, together with Monte Carlo modeling simulations for various underwater scenarios, yields an optimal optical layout, and analyses of the efficiencies, S/N and resolution capabilities. We develop a preliminary packaging concept for a small underwater vehicle, together with size and weight estimates. In the Option, we define the electronics and interfaces, and develop a power budget for the complete system. The Phase I preliminary design leads to detailed design and construction of a prototype in Phase II.