Determination of Hurst exponent by optical signal processing applied on surface roughness measurements

In this work a surface roughness measurement performed by Hurst exponent determination, calculated at the same time from data processing of an optical reflected signal is presented. An industrial plate roller rod covered with a polymeric coating is illuminated using a laser source. A lens is used for casting the scattered light reflected from several sectors of the plate roller, and also to focus it into a power meter connected to a computer where corresponding data series are stored. Information related to specific points of the considered object is contained into the optical reflected signal and post-processing of related data signal series allows calculation of the Hurst exponent, also known as roughness exponent. A wear analysis on considered surface sectors of the roller is performed and as a result a relation between Hurst exponent and the coating thickness for each surface sector is clearly established. The simplicity of the opto-mechanical setup among other evident advantages may suggest the application of this non-destructive technique on surface metrology.