Scanning Optical Coherence Tomography Applied to the Characterization of Surfaces and Coatings

Abstract

This paper shows the technique of optical coherence tomography in the frequency domain (OCT-FD) to obtain surfacetopography and tomography of surface coatings. The setup is based on a superluminescent diode centered on 849 nm with anspectral wide of 50 nm as the light source, a single-mode fibre Michelson interferometer and a spectrometer as the detectorsystem. This scheme allows having compact and robust equipments that was designed to be used in an industrial environment.With this system it can be obtain a tridimensional image acquired point by point with a maximum range of 20 mm width andlength and 2 mm depth. Images obtained from the topography of metal samples and tomography of polymer based coatings ispresented. Also it is shown that is possible to obtain, from these images, parameters of interest of the sample, such as roughness,flatness and characteristic distances. As an example to show the potential of the method the dimensions of a metal surfacemodified after laser ablation were measured from a topography image obtained with this technique. A second example presentedwas the image obtained of a roughness pattern made on a metal surface. Finally it was presented a tomography image of amodified polyurethane coating deposited on a metal surface. Thickness and refractive index of the coating were obtained after theimage analysis.