The interferometer is the core of every Fourier-transform spectrometer. Today's FT spectrometers use a variety of interferometer designs. However, they are all still based on the simple, yet historically most important, Michelson interferometer.
In this chapter, the operating principle of the Michelson interferometer for FT spectroscopy is discussed. It is the objective of this chapter to provide a thorough physical understanding of how a spectrum is generated in an FT spectrometer. Enough mathematics is used to aid comprehension. First, a qualitative overview is provided, which is followed by a more detailed explanation starting with the wave description of light. Then, the factors that limit the output spectral resolution are explored, and finally, the interferogram processing techniques sometimes necessary to obtain accurate spectra are briefly discussed.
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