Interferometric Subsurface Evaluation System

Accurate detection of subsurface corrosion and other defects in aircraft can prevent serious damage to multimillion-dollar machinery and save lives. The Air Force therefore has a need for an easily operated, portable non-destructive evaluation (NDE) system that can detect, identify, and localize subsurface defects. To address this need, Physical Optics Corporation (POC) proposes to develop a novel Interferometric Subsurface Evaluation System (ISES), which will significantly improve on current NDE methods. The proposed ISES implements a phase conjugate Michelson interferometer to measure surface nanodeflection, combined with a novel optical phase-stepping technique and thermal pulsing. The ISES will be rugged, able to operate in the field, and highly reliable, unlike current ultrasonic NDE equipment. It will accurately detect and localize subsurface defects, unlike current interferometric and holographic NDE testing systems. The ISES will rapidly and accurately detect corrosion areas less than 0.030 inch in size in multilayer materials up to 0.5 inch thick. In Phase I POC will demonstrate the feasibility of ISES by developing and testing a laboratory prototype, and showing that it can detect and localize known defects in multilayer materials. In Phase II POC plans to develop a functional prototype for demonstration at an Air Force test site.