Terahertz Imaging for Detection of Corrosion and Defects Under Hull Coatings

In this Phase I SBIR project we propose to demonstrate the key elements of a practical, field-deployable non-contact time-domain terahertz (TD-THz) system for rapid detection of submarine hull defects such as corrosion and gouges hidden beneath acoustic hull coatings, hull coating material defects, and hull coating adhesion defects. The key feasibility areas addressed will be developing the high-resolution focusing system required for the high contrast detection of flaws on the hull-coating interface buried several inches beneath the surface; and utilizing this focusing lens assembly in a novel TD-THz scanner system which can rapidly image large areas of a submarine hull in a shipyard environment. TD-THz is a non-contact imaging method which has been shown to detect corrosion and volume defects. The ultra-wideband pulsed TD-THz reflection tomography method allows in-situ inspection through hull coatings, since these polymeric coatings transmit in the THz band. The TD-THz pulse reflections can be focused and collected with high numerical aperture lenses, and time-gated at the buried hull-coating interface for precise, high contrast 3D-layer sub-surface imaging.