Simultaneously measuring the refractive index and thickness of an optical sample by using improved fiber-based optical coherence tomography

Yen, Chih Ta; Huang, Jen-Fa; Wu, Ming; Lee, Yu Fan; Huang, Chia Tsai; Huang, Shu Pin; Cheng, Hsu-Chih

doi:10.1117/1.oe.53.4.044108

Cited by 5 publications

(2 citation statements)

References 17 publications

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“…Besides medical and pharmaceutical applications, low coherence interferometry (upon which OCT is based) can be used to measure coating thickness (Kühnhold et al, 2015;Manallah et al, 2015) and optical properties of polymer films, such as topography (Ghim et al, 2013), roughness (Yoshino et al, 2017) and refractive indices (Yen et al, 2014). Also inline monitoring of coating process applications in industrial coaters (both for tablets and pellets) have been demonstrated (Sacher et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

At-line validation of optical coherence tomography as in-line/at-line coating thickness measurement method

Wolfgang

Anna

Wahl

et al. 2019

International Journal of Pharmaceutics

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Optical Coherence Tomography (OCT) is a promising technology for monitoring of pharmaceutical coating processes. However, the pharmaceutical development and manufacturing require a periodic validation of the sensor's accuracy. For this purpose, we propose polyethylene terephthalate (PET) films as a model system, which can be periodically measured during manufacturing coating monitoring via OCT. This study proposes a new approach addressing the method validation requirement in the pharmaceutical industry and presents results for complementary methods. The methods investigated include direct measurement of the layer thickness using a micrometer gauge as reference, X-ray micro computed tomography, transmission and reflectance terahertz pulsed imaging, as well as 1D-and 3D-OCT. To quantify the significance of OCT for pharmaceutical coatings, we compared the OCT results for commercial Thrombo-ASS and Pantoloc tablets with direct measurements of coating thickness via light microscopy of microtome cuts. The results of both methods correlate very well, indicating high intraand inter-tablet variations in the coating thickness for the commercial tablets. The light microscopy average measured coating thickness of Thrombo-ASS (Pantoloc) was 71.0 µm (83.7 µm), with an intercoating variability of 8.7 µm (6.5 µm) and an intra-coating variability of 2.3 µm to 9.4 µm (2.1 µm to 6.7 µm).

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Section: Introductionmentioning

confidence: 99%

At-line validation of optical coherence tomography as in-line/at-line coating thickness measurement method

Wolfgang

Anna

Wahl

et al. 2019

International Journal of Pharmaceutics

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“…Several techniques have been reported for simultaneous measurement of refractive index and thickness using an OCT system in both TD and FD. These techniques suitable for single layer objects can be listed in TD as low-coherence reflectometry, [14][15][16][17][18] focus-tracking method, [19][20][21][22][23][24][25][26][27][28][29] bifocal optical coherence refractometry, 30,31 digital refocusing technique, 32,33 and tandem configuration of interferometers for dispersion-insensitive measurements. [34][35][36] In the FD approach, the simultaneous measurement of refractive index and thickness of a single layer object has been reported using a reference plane behind the object, 37,38 providing a step on the object, 39 using a dual sample probe 40 or by fitting a modeled signal to the actual spectrum.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography, part 1: theory

et al. 2017

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We introduce a theoretical framework for simultaneous refractive index and thickness measurement of multilayer systems using the Fourier domain optical coherence tomography (FD-OCT) system without any previous information about the item under investigation. The input data to the new formalism are the FD-OCT measured optical path lengths and properly selected spectral components of the FD-OCT interference spectrum. No additional arrangement, reference reflector, or mechanical scanning is needed in this approach. Simulation results show that the accuracy of the extracted parameters depends on the index contrast of the sample while it is insensitive to the sample’s thickness profile. For transparent biological samples with smooth interfaces, when the object is in an aqueous medium and has indices < 1.55 , this method can extract indices and thicknesses with the absolute error ? 0.001 .

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Measurement of Thickness and Refractive Index of Optical Samples Simultaneously Using Full-Range One-Shot Frequency-Domain Optical Coherence Tomography

Cheng

Huang

2015

Fiber and Integrated Optics

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Simultaneously measuring the refractive index and thickness of an optical sample by using improved fiber-based optical coherence tomography

Cited by 5 publications

References 17 publications

At-line validation of optical coherence tomography as in-line/at-line coating thickness measurement method

At-line validation of optical coherence tomography as in-line/at-line coating thickness measurement method

Simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography, part 1: theory

Measurement of Thickness and Refractive Index of Optical Samples Simultaneously Using Full-Range One-Shot Frequency-Domain Optical Coherence Tomography

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