Shedding light on coatings: Real-time monitoring of coating quality at industrial scale

Optical Coherence Tomography (OCT) is increasingly being used for studies of pharmaceutical film coating. OCT allows fast and non-destructive analysis of the coating thickness and quality via high-resolution cross-sectional images. Information about both the coating thickness and the coating quality can be extracted. Most studies and OCT applications performed to date have been limited to off-line measurements and off-line computations of coating features based on data acquired in-line. This study examines OCT's applicability to an industrial-scale pan coating process. Automated layer detection, classification and thickness calculation were executed in real time. To evaluate the system's performance, runs with various tablet size, coating solution concentration and operating parameters were carried out and monitored. Our results indicate that, in addition to correct end-point determination, OCT enables real-time monitoring of the coating processes (thickness, homogeneity and roughness) and can support active process control by supplying information about the coating thickness and quality.