Editing Michelson interferometer (section)

===Fourier transform spectrometer===
{{main|Fourier transform spectroscopy}}

Fig.&nbsp;5 illustrates the operation of a Fourier transform spectrometer, which is essentially a Michelson interferometer with one movable mirror. (A practical Fourier transform spectrometer would substitute [[Corner reflector|corner cube reflectors]] for the flat mirrors of the conventional Michelson interferometer, but for simplicity, the illustration does not show this.) An interferogram is generated by making measurements of the signal at many discrete positions of the moving mirror. A [[Fourier transform]] converts the interferogram into an actual spectrum.<ref name=OPIFourier>{{cite web|title=Spectrometry by Fourier transform|url=http://www.optique-ingenieur.org/en/courses/OPI_ang_M02_C05/co/Contenu_32.html|publisher=OPI - Optique pour l'Ingénieur|access-date=3 April 2012}}</ref> Fourier transform spectrometers can offer significant advantages over dispersive (i.e., grating and prism) spectrometers under certain conditions. (1) The Michelson interferometer's detector in effect monitors all wavelengths simultaneously throughout the entire measurement. When using a noisy detector, such as at infrared wavelengths, this offers an increase in [[signal-to-noise ratio]] while using only a single detector element; (2) the interferometer does not require a limited aperture as do grating or prism spectrometers, which require the incoming light to pass through a narrow slit in order to achieve high spectral resolution. This is an advantage when the incoming light is not of a single spatial mode.<ref name=Block>{{cite web|title=Michelson Interferometer Operation|url=http://blockeng.com/technology/ftirtechnology.html|publisher=Block Engineering|access-date=26 April 2012}}</ref> For more information, see [[Fellgett's advantage]].