The Application of Full-Field Optical Coherence Tomography on Evaluating Film Coating of Pharmaceutical Pellets

This paper focuses on the application of full-field optical coherence tomography (FF-OCT) imaging on quantifying coating thickness and characterizing coating structures of two-layer pharmaceutical pellets. This FF-OCT system used an inexpensive infrared light-emitting diode (LED) as the optical source and a commercial high speed complementary metal-oxide semiconductor (CMOS) camera as the detector. A total volume of 700 × 50 × 200 μm³ (x-y-z) were imaged by using the FF-OCT device. A high spatial resolution of 4.0 × 5.0 μm² (axial × lateral) was achieved. In the cross-sectional image the internal structure details can be clearly observed and in particular particle-like features can be clearly resolved. In order to quantify the coating thickness, the scanned area was divided into 48 groups of small cell, the coating thickness in each cells was calculated automatically and the mean film coating thicknesses were 39.7 ± 7.3 μm and 49.1 ± 7.0 μm for the outer layer and inner layer respectively. These results demonstrate the potential of FF-OCT system as a non-destructive and no-contact imaging tool for analyzing film coatings of pharmaceutical pellet samples.