2 August 2010 Comparison of different film thickness evaluation algorithms applicable to spectrometric interrogation systems
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There are various methods for film thickness measurement. This paper aims at thin film measurement methods which work with wavelength-dependent sensor signals, no matter how the signal was captured. These measurement systems are called Thin Film Reflectometers (TFR). The resolution of thin film reflection measurement is limited by the spectral resolution of the detection system, the spectral wavelength range and the analyzing algorithm. Analytical theory of four different algorithms for thin film measurement is described and algorithms are compared via numerical simulations. Most of these algorithms can be found both in the literature and in different software-libraries (e.g. MATLAB, LabVIEW...) To compare different algorithms, the reflected light intensities of a thin film have been simulated for an exemplary thin glass film and a common off-the-shelf-spectrometer, a broadband visible light source and characteristic noise levels. The same data was fed for four selected algorithms in order to compare the results. To characterize algorithms in resolution, range and accuracy, the standard deviation of the output data has been computed for different spectral windows and resolutions. As a result we can provide a concise recommendation for appropriate use of the presented TFR algorithms.
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Florian Hirth, Florian Hirth, Ana Pérez Grassi, Ana Pérez Grassi, Daniel G. Dorigo, Daniel G. Dorigo, Alexander W. Koch, Alexander W. Koch, "Comparison of different film thickness evaluation algorithms applicable to spectrometric interrogation systems", Proc. SPIE 7790, Interferometry XV: Techniques and Analysis, 77900V (2 August 2010); doi: 10.1117/12.859687; https://doi.org/10.1117/12.859687

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