Surface profile inspection for large structures with laser scanning

Fringe projection profilometry is a powerful tool that is widely applied to shape measurement of objects in engineering. Limited by the light intensity of the projection unit, this technique is difficult to be applied to surface inspection of large structures, especially in outdoor applications. In this study, a line laser source is selected as the light projection unit. The line laser beam is controlled to scan the surface with the predefined angular speed while a stationary imaging unit captures images. An image fusion strategy has been proposed to construct grating images with a constant phase shift, which facilitates full-field phase shifting in determination of the structural profile. The accuracy of the measurement method is discussed and compared with a commercial 3D laser scanner. The proposed technique has also been applied to the surface topography of the wind turbine blades. The experimental results show that the bulging defects on the surface of the wind turbine blade model are detectable, which shows the feasibility of the proposed method in characterization of surface profile on large structures.