Optical coherence tomography as a novel tool for in-line monitoring of a pharmaceutical film-coating process

Daniel Markl, Günther Hannesschläger, Stephan Sacher, Michael Leitner, Johannes G. Khinast

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)


Optical coherence tomography (OCT) is a contact-free non-destructive high-resolution imaging technique based on low-coherence interferometry. This study investigates the application of spectral-domain OCT as an in-line quality control tool for monitoring pharmaceutical film-coated tablets. OCT images of several commercially-available film-coated tablets of different shapes, formulations and coating thicknesses were captured off-line using two OCT systems with centre wavelengths of 830 nm and 1325 nm. Based on the off-line image evaluation, another OCT system operating at a shorter wavelength was selected to study the feasibility of OCT as an in-line monitoring method. Since in spectral-domain OCT motion artefacts can occur as a result of the tablet or sensor head movement, a basic understanding of the relationship between the tablet speed and the motion effects is essential for correct quantifying and qualifying of the tablet coating. Experimental data was acquired by moving the sensor head of the OCT system across a static tablet bed. Although examining the homogeneity of the coating turned more difficult with increasing transverse speed of the tablets, the determination of the coating thickness was still highly accurate at a speed up to 0.7 m/s. The presented OCT setup enables the investigation of the intra- and inter-tablet coating uniformity in-line during the coating process.

Original languageEnglish
Pages (from-to)58-67
Number of pages10
JournalEuropean Journal of Pharmaceutical Sciences
Issue number1
Publication statusPublished - 13 May 2014


  • in-line monitoring
  • non-destructive testing
  • optical coherence tomography
  • pharmaceutical film-coated tablets
  • quality control

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