Optimising laser-induced phased-arrays for defect detection in continuous inspections

This paper proposes a novel optimisation approach for laser induced phased-arrays for detection purposes in large area inspection. The optimisation aims to maximise the detection capability of a phased-array while minimising the inspection time. This is done by using a simulation ray-tracing model that evaluates multiple candidate configurations. The metrics that measure the detection performance for a target defect are the receiver operating characteristic curve and the signal-to-noise ratio. The inspection time is indirectly computed through the number of measurement points per unit length in a continuous inspection. This depends on the physical aperture and pitch of the phased-array and they are the quantities optimised. The optimisation and modelling approach are validated in an experimental case study for a side-drilled hole as target defect. Further recommendations about directional defects (e.g. cracks at different angles) are provided.