文档介绍：area of the beam at any focus-that is,
the throughput, is greater for an interfer-
ometer than for a monochromator.
For interferograms to be transformed
into spectra, they must be digitized. In
essentially all modern Fourier transform
Fourier Transform infrared (FTIR) spectrometers, this goal
is achieved by sampling at equal inter-
Infrared Spectrometry vals of optical path difference using the
sinusoidal interferogram from a helium-
neon laser beam which is passed through
Peter R. Griffiths a different region of the beamsplitter of
the interferometer. The infrared interfer-
ogram is generally digitized once per
wavelength of the laser interferogram
The origin of Fourier transform tech- lengths even at the centerburst, so that a (typically at a zero-crossing). This meth-
niques for the measurement of high-qual- typical "real" interferogram in this re- od of sampling gives rise to the third
ity infrared spectra can be traced back to gion is not symmetrical, but usually has major advantage of FTIR spectrometry,
the turn of the century, when Michelson the form shown in Fig. lA. which is its extremely high wave number
first described the interferometer that The interferogram is related to the precision.
now bears his name (1). In this instru- spectrum through its Fourier transform A fourth benefit, which results in part
ment an input collimated b