Non-Destructive Measurement of Micro Coating Thickness Using Sweep Frequency Photoacoustic Sensing

Title: Non-Destructive Measurement of Micro Coating Thickness Using Sweep Frequency Photoacoustic Sensing Technique
Author: Abhijeet Gorey, Chirabrata Bhaumik, Tapas Chakravarty, Annesha Mazumder, Arijit Sinharay, Subhadeep Basu, Rajat Das, Arpan Pal
Affiliation: TATA Consultancy Services Limited , India
Abstract: Non-destructive and rapid measurement of micro coating thickness is a challenge for most of the paint coating industries. This study proposes a novel sweep frequency photoacoustic sensing technique for the non-destructive estimation of a coating layer thickness. The continuous wave laser diode used for the sample excitation makes the overall system compact and portable. Also, the usage of frequency sweep enables the technique to be applied to different substrates and different coating layers. The Rosencwaig-Gersho (RG) model is employed to estimate the thickness of the coating layer by measuring the resonance frequency of the photoacoustic wave. Regression analysis is performed to obtain the micro thickness through photoacoustic measurements. The photoacoustic measurements are compared with the standard (cross-sectional microscopy) thickness measurement technique and the error is found to be less than 5%. The simple computational method and instrumentation used in this technique enable it to be deployed in industries for rapid estimation of the micro thickness.