Multi-channel random-quadrature receiver for industrial laser-ultrasonics

We recently introduced a laser-based ultrasonic (LBU) receiver based on multi-channel random-quadrature (MCRQ) detection. MRCQ receiver was specifically developed to meet the demanding needs of industrial inspections where operating conditions are far from ideal. We showed that by integrating detector arrays into a classic interferometer design, we can transform a high-sensitivity but delicate laboratory interferometer into a rugged system capable of enduring tough industrial environment. MCRQ detection can be implemented using either a free-space or a fiber optical designs, without reduction in performances. Initially, the ultrasonic information was extracted with simple and very robust signal processing based on high-pass filtering followed by signal rectification. We recently introduced a new demodulation scheme which allows for linear detection. Linear detection is based on phase-flip correction achieved via lock-in detection of a known perturbation signal.