2D Laser-Induced Phased Arrays for Large-Area Scans Using Poisson-Disk Layouts

Abstract

There is an increased need for the development of reliable non-contact non- destructive evaluation (NDE) techniques which can be deployed using machines/robots in remote locations and risk-associated environments. This work suggests a new ultrasound scanning technique for large areas using 2D laser-induced phased arrays (LIPAs). The objective is to achieve a given detection sensitivity using the smallest possible number of measurements. This reduces the scanning time, size of the collected data, and energy usage. Bridson Poisson sampling is proposed to define both the generation-laser aperture relative to a single detection point (physical aperture) and the detection-laser scanning points over an arbitrary inspection surface. The proposed imaging solution is based on the total focusing method (TFM) but differs from conventional and previous LIPA solutions. The full matrix capture (FMC) for each imaging location on the surface, referred to as the region of interest (ROI), is determined by the available detection points within its vicinity. This vicinity is expressed by a specific radius, defining the size of the computational aperture. The proposed methodology is analytically evaluated using ray-tracing model simulations. Poisson- disk sampling is compared to regular-shaped (square and triangular) grids, demonstrating its clear superiority in both detection/imaging performance and scanning time. Recommendations for optimisation and experimental validation are suggested for future work.