Laser-Induced Full-Matrix Ultrasonic Imaging of Complex-Shaped Objects

We present laser-induced full-matrix imaging of complex-shaped objects that combines the advantages of noncontact laser ultrasound inspection and high-contrast array imaging based on total focusing method (TFM). Full-matrix data were acquired by synthesizing a laser ultrasonic array through an alternate scanning of the generation and detection laser beams. Taking advantage of the simultaneous generation of all wave modes, surface Rayleigh waves were extracted for surface profiling, and longitudinal waves were utilized for imaging. To gain a better understanding, we analyzed the full-wave dynamics in generation, propagation, and scattering by using numerical simulations. TFM was adapted to accommodate complex surface and suppress interference from other waves, including surface waves and straightforward traveling bulk waves between emission and reception. Numerical and experimental studies on an aluminum sample with a sinusoidal surface and side-drilled holes were conducted, and results agreed well.