Spectral Background Removal of MEMS FTIR Spectrometer-Based Gas Analyzer

摘要

The wide spectral range, compactness, low cost and high measurement speed of the MEMS FTIR spectrometersenable their use in real-time in-line gas analysis. They have the potential of identifying and quantifying several gasessimultaneously compared to other infrared technologies such as the NDIR. However, the challenge of real-timespectral background removal from the measured spectrum has to be tackled first. In fact background removal is acommon problem to spectroscopic applications relaying on the spectral shape and strength of the absorption lines. Inthis work, two of the most recent background correction algorithms, namely iterative averaging and morphologicalweighted penalized least squares, are adapted and applied on the MEMS FTIR spectrometer for gas mixtureanalysis. These algorithms don’t require prior knowledge about the background or the peaks position and don’tinvolve any manual selection of a suitable local minimum value. A 10-cm gas cell that contains knownconcentrations of SO_2, C_2H_4, N_2O and N_2 was measured using the MEMS FTIR spectrometer. The presence ofseveral spectral absorption lines of these gases in the mid-infrared (MIR) region is considered a challenging case forautomatic background correction algorithms. The spectra are measured in the MIR range of 1.6 μm - 4.9 μm with aresolution down to 33 cm~(-1). The corrected spectra are compared with spectra measured with a standard bench-topspectrometer and the RMS error and Pearson’s correlation coefficient are calculated and good values of 0.8 % and98 %, respectively, are obtained. Overcoming the spectral background removal paves the way for the use of MEMSFTIR spectrometer in real-time monitoring of multiple gases simultaneously.