Mapping of ultrasonic thickness measurements using laser grid projection and image processing

A three-dimensional surface mapping method for ultrasonic thickness measurements is proposed to enable the dimensions and positions of measured values obtained by the conventional ultrasonic thickness gauges and flaw detectors on curved surfaces to be determined. The proposed system consists of a laser pattern generator and image processing methods. The laser grid produced by the pattern generator is projected onto the surface of the item to be inspected, mathematical relationships are developed to localise the grid nodes on the inspection surface and images are then captured using a complementary metal-oxide semiconductor (CMOS) camera. An image processing algorithm is developed to plot the scanned surface. The measurements performed using a thickness gauge are correlated with the plotted surface, which will enable thickness mapping. The experiments were carried out on a pipe with an artificial metal loss defect and the results showed that the developed method can accurately locate measured thickness values on a three-dimensional plotted surface.