Contouring of artwork surface by fringe projection and FFT analysis

In the present work, we propose a simple optical method to perform profilom etry on works of art. The method is based on the projection of a Ronchi gra ting onto the surface to be analyzed. When viewed at an angle different fro m the projection angle, the grid pattern appears deformed by the surface sh ape. This pattern is digitized, by a high-resolution CCD camera, and then p rocessed using a Fourier transform analysis. The technique is free from the errors caused by higher harmonic components of the grating pattern. Furthe rmore, the method relies on very simple equipment and it is therefore suita ble for in situ measurements. Theoretical details and examples of the techn ique in operation are given. (C) 2000 Elsevier Science Ltd. All rights rese rved.