Quantification of thin-film coating thickness of pharmaceutical tablets using wavelet analysis of terahertz pulsed imaging data

Terahertz pulsed imaging (TPI) is a powerful tool for nondestructive and quantitative characterization of pharmaceutical tablet coatings. In this paper, we present various processing methods for determining coating thickness from the measured terahertz waveform. We demonstrate that a wavelet-based method can be used to characterize the tablet coating with a thickness down to 25 microns, which is better than a conventional “peak-finding” method. Experimental results demonstrated that this new method is also applicable to real-time in-situ monitoring and control of pharmaceutical manufacture processes.