Thickness Measurement of Tablet Coating using Continuous Wave Terahertz Reflection Spectroscopy

摘要

THz rays have higher penetration depth compared to infrared rays and hence can be effectively used to measure tablet coating thickness. In addition, THz wavelength (1 mm - 0.1 mm) provides an optimal depth resolution for the thickness measurement. This method can be non-invasive and hence ideal for inline quality monitoring. Tablet coating thickness is one of the major parameters of interest in Process Analytical Technology (PAT). In this paper, a reflection mode Continuous Wave (CW) Terahertz (THz) system has been employed to measure the tablet coating thickness. A frequency scan of the sample has been carried out from 0.1 THz to 1.1 THz and the reflection coefficient of the sample is inverse fourier transformed to obtain the tablet thickness. The calculated thickness has also been validated using the optical microscope. Results show that the thickness can be measured with considerable accuracy.