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

Abstract

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 .

Dual-angle optical coherence tomography for index of refraction estimation using rigid registration and cross-correlation

“…14 Recently, a new study formulated a new method, using FD-OCT measured optical path lengths (OPLs) and properly selected spectral components of FD-OCT interference spectrum, to simultaneously measure path length and index of refraction. 15 However, this method has not been demonstrated in vivo and the authors expressed concerns regarding the detrimental effects of speckle and beam aberrations caused by tissue.…”

Simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography, part 2: implementation

“…In conclusion, we introduced in this article (together with its first part) 44 a framework for simultaneous extraction of refractive index and thickness of transparent multilayer systems without any previous information about the item under investigation from its FD-OCT data. No additional arrangement, reference reflector, or mechanical scanning is needed, which is the main advantage of this approach.…”

“…A framework for selecting the suitable spectral components in the presence of ε was given in the first part of this article. 43,44 The impact of increasing ε on the parameter extraction is investigated in this article to find out what is the maximum ε that still allows the extraction of the parameters and how much is the accuracy loss in each parameter as ε increases.…”

“…3.2. 44 Both layers thickness is fixed at 30 μm and the optical paths measurement error of ε 1;2 ¼ þ0.1 μm is induced for both layers. The test models are generated with n 1 and n 2 varying from 1.337 to 1.9 in 0.011 increments (total number of 2600 test models) while n 3 ¼ 1.337 but must still be extracted by the software.…”

Index of refraction estimation using dual-angle optical coherence tomography

“…Using OCT, a common method to estimate n is based on measuring the path-length change from a sample placed over a reflector but is only appropriate for ex vivo measurements 9 . Other methods, that have been recently proposed, depend on very complicated experimental setups and algorithms and are also very hard to apply in vivo [10][11] . A new method, appropriate for in vivo and in situ measurement of n in tissues, without the need for a reflector as a reference, is proposed here.…”