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Bruker Optik GmbH IFS 125M User Manual
Glossary F
Interferogram The interferogram is a plot of detector signal as a function of
optical path length difference. Spectrometers are equipped
with a broadband light source, which yields a continuous infi
-
nite number of wavelengths. The interferogram is the continu-
ous sum, i.e. the integral of all the interference patterns
produced by each wavelength. This results in the intensity
curve as function of the optical retardation.
At the zero path difference of the interferometer ( x=0) all
wavelengths undergo constructive interference and sum to a
maximum signal. As the optical retardation increases different
wavelengths undergo constructive and destructive interference
at different points, and the intensity therefore changes with
retardation. For a broadband source, however, all the interfer
-
ence patterns will never be simultaneously in phase except at
the point of zero path difference, and the maximum signal
occurs only at this point. This maximum in the signal is referred
to as the centerburst. Dispersive elements detected in the opti
-
cal path can cause chirping in the centerburst.
Interferometer An interferometer detects interferences, that means overlap-
pings of light waves. Inside the interferometer a light beam is
splitted into two light waves (beams) by the beam splitter.
These two light waves pass through optical paths of different
lengths, are reflected by additional mirros, and finally recom
-
bined.
If you change the optical path of one of the two light waves,
e.g. by moving one mirror, the phases of the two light waves
displace against each other. When recombining the light
waves, interferences occur.
The result is an interference pattern (stripes or rings) which
has been written by the light waves. This pattern is determined
by the difference of the optical path lengths which the single
light waves have passed before being recombined.
IP address An IP address is the network address of a workstation or net-
work. IP addresses consist of 4 number fields separated by
dots. Each number field represents 1 byte. Values can be
between 0 and 255. The numbers on the left of the string
define the network, the numbers on the right define the individ
-
ual workstation or Network Interface Card (NIC).
Lambert-Beer Law Linear approximation for the relation between the absorbance
of a sample and its concentration used to predict unknown
concentrations. Mathematically expressed by A = abc, where A
represents absorbance, a, b, and c are absorptivity or extinc
-
tion coefficient, path length and concentration.
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