PerkinElmer Frontier Optica FT-IR, Руководство пользователя

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54 . Frontier Optica FT-IR User's Guide
Phase correction
Phase correction is a necessary part of the process of converting the measured interferogram
into a spectrum. There are three options available:
Background
Background uses the information in the interferogram of the background scan to correct
both the background and sample spectra.
This is the recommended option for optical measurements.
If there is a long time delay between background and sample measurements this could
introduce errors. In this case, it is advisable to collect a new background before your sample
spectrum.
Magnitude
Magnitude is not suitable when transmittance values very close to zero have to be
measured. Any transmittance values that are negative due to noise will be rectified to appear
positive. This will result in average values that are offset to be slightly above zero, with the
size of the offset depending on the noise level. This problem can be avoided by using
Background phase correction.
Self
Self
uses the background and sample interferograms separately to correct the respective
spectra. As with Magnitude, there can be problems when transmittance values are close to
zero. There is no phase information from regions where transmittance is zero, leading to
inaccurate transmittance values in those regions and in sharp band edges adjoining these
regions. This problem can be avoided by using Background phase correction.
NOTE: Phase correction is set on the Setup Instrument Advanced tab in Spectrum software
(Figure 14). See the on-screen Help for more information.
Apodization
The true interferogram of a light source is infinite in length. A spectrometer can only
measure a finite part of the interferogram. This means that unwanted oscillations or
sidelobes are produced on either side of narrow bands in the spectrum. Apodization is a
mathematical function applied to the interferogram to remove the sidelobes. The influence of
apodization on lineshape may become important when, for example, measuring narrow
passband filters.
The Spectrum software has a number of types of Apodization available.
For optical measurements we recommend Filler . The Apodization function is defined on the
Setup Instrument Advanced Tab (Figure 14).
Please refer to the Spectrum on-screen Help for more information.