Description of a Standard FTIR Instrument

In FTIR spectroscopy, an interference wave interacts with the sample in contrast to a dispersive instrument where the interacting energy assumes a well-defined wavelength range. The interference wave is produced in an interferometer (Fig. 4.1.1), the most common of which is the Michelson interferometer. A computer is used to control the interferometer, to collect and store data, and to perform the Fourier transformation. In addition, the computer performs post-spectroscopic operations such as spectral presentation, resolution enhancement, calibration, and calculation of correlation equations. 

A collimated light beam from the 1R source is directed to the Michelson interferometer where it is divided by the beam splitter. One half of the beam is reflected from a fixed mirror and the other half from a moving mirror. The two light beams recombine after returning from the mirrors and give rise to a reconstructed beam which is optically an interference wave. The interference light beam passes through the sample and is modified by its interaction with the 

Springer Series in Wood Science Methods in Lignin Chemistry (Edited by S.Y. Lin and C.W. Dence) 

Fourier transformation is a decoding procedure by which the signal is converted from the so-called time domain, where the signal is a function of retardation, to the frequence domain, where it is a function of frequency, according to the formula  

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