Real-time data processing for in-line monitoring of a pharmaceutical coating process by optical coherence tomography

Daniel Markl, Jakob Ziegler, Günther Hannesschläger, Stephan Sacher, Andreas Buchsbaum, Michael Leitner, Johannes G. Khinast

Research output: Contribution to journalConference Contributionpeer-review

1 Citation (Scopus)


Coating of tablets is a widely applied unit operation in the pharmaceutical industry. Thickness and uniformity of the coating layer are crucial for efficacy as well as for compliance. Not only due to different initiatives it is thus essential to monitor and control the coating process in-line. Optical coherence tomography (OCT) was already shown in previous works to be a suitable candidate for in-line monitoring of coating processes. However, to utilize the full potential of the OCT technology an automatic evaluation of the OCT measurements is essential. The automatic evaluation is currently implemented in MATLAB and includes several steps: (1) extraction of features of each A-scan, (2) classification of Ascan measurements based on their features, (3) detection of interfaces (air/coating and coating/tablet core), (4) correction of distortions due to the curvature of the bi-convex tablets and the oblique orientation of the tablets, and (5) determining the coating thickness. The algorithm is tested on OCT data acquired by moving the sensor head of the OCT system across a static tablet bed. The coating thickness variations of single tablets (i.e., intra-tablet coating variability) can additionally be analyzed as OCT allows the measurement of the coating thickness on multiple displaced positions on one single tablet. Specifically, the information about those parameters emphasizes the high capability of the OCT technology to improve process understanding and to assure a high product quality.

Original languageEnglish
Article number91290M
Number of pages10
JournalProceedings of SPIE
Publication statusPublished - 8 May 2014
EventBiophotonics: Photonic Solutions for Better Health Care IV - Brussels, Belgium
Duration: 14 Apr 201417 Apr 2014


  • in-line monitoring
  • optical coherence tomography
  • pharmaceutical coating process
  • real-time data processing


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