Refractometric low coherence interferometry applied for mixture analysis

Abstract

This thesis analysis low coherence interferometry as a tool for the study of mixtures. It is mainly based on Dispersion Interferometry (DI) technique. Spectral phase analysis of different concentrations of pure solutions have been used to determine the dispersion behavior in the range of 0.550 - 0.850 µm and form a basis to evaluate sensitivity of these substances' dispersion to concentration. Afterwards the classical linear analysis method has been used to differentiate and estimate their concentrations in a complex solution. As an other application of Dispersion Interferometry, in a first step presented here, sample dispersion data have been used for absolute depth or thickness measurement of dispersive samples. The measurements are based on dispersion data of the samples, so the method can be introduced with the term Dispersion Interferometry (DI). In order to verify accuracy and validity of that technique, glass samples of known thickness have been studied. Dispersion of microscope cover glass plates (~140 µm) have been measured and used to generate and calibrate a scale for thickness measurements. Afterwards, a carrier glass plate was used as an unknown thickness. Result of the measurement with DI technique was in a good agreement with the reality, as a discrepancy of 3 µm was observed, i.e. an accuracy of around 2 %. According to the results, it seems that parallel to the other low coherence interferometry methods, DI can be considered as a promising technique for depth and thickness measurements. Its advantage is the ability of absolute thickness/depth measurement, so abandons the need for a reference location at the sample where to other scattering surfaces are relatively ranged, furthermore, independency of the measurement from axial movement of the sample.