Micro-Optical Sensors for Underwater Velocity Measurement

This manuscript describes recent progress in the development and fielding of optical MEMS-based Mini-and Micro-sensors for surface and underwater applications. The non-intrusive sensors have been developed to measure vehicle speed, boundary layer velocity profile, and skin friction. The MiniLDV^TM and Micro velocimeters have been used as a speed sensor in torpedoes, scaled submarines, and surface vessels at sea and in tow tanks. The same instruments have also been used for boundary layer profilometry at variety of Reynolds numbers. MicroS^TM shear stress sensors have been used for drag reduction studies in full-scale sea trials. The small size and integrated electronics of the micro-sensors make them especially appropriate for applications in UUV and AUV. In all cases, particles present in the ocean water were found to be adequate both in concentration and size as scattering sources for the measurement. The building blocks for MEMS-based optical sensors are described and examples of sea trials are presented.