Combining Cubic Spline Interpolation and Fast Fourier Transform to Extend Measuring Range of Reflectometry
Ju Cheng1,2, Jian Lu1**, Hong-Chao Zhang1, Feng Lei2**, Maryam Sardar1, Xin-Tian Bian2, Fen Zuo2, Zhong-Hua Shen1, Xiao-Wu Ni1, Jin Shi2
1School of Science, Nanjing University of Science and Technology, Nanjing 210094 2School of Physics and Electronic Electrical Engineering, Huaiyin Normal University, Huai'an 223001
Abstract：The reflectometry is a common method used to measure the thickness of thin films. Using a conventional method, its measurable range is limited due to the low resolution of the current spectrometer embedded in the reflectometer. We present a simple method, using cubic spline interpolation to resample the spectrum with a high resolution, to extend the measurable transparent film thickness. A large measuring range up to 385 μm in optical thickness is achieved with the commonly used system. The numerical calculation and experimental results demonstrate that using the FFT method combined with cubic spline interpolation resampling in reflectrometry, a simple, easy-to-operate, economic measuring system can be achieved with high measuring accuracy and replicability.
2018, Vol. 35 
