Bomem-GRAMS User's Guide

Appendix D
Glossary
To avoid channel spectrum in transmission cells with a small optical
pathlength, a wedge in the sample path is used to prevent parallelism of the
two windows.
coadded spectrum
The spectrum resulting from averaging, on a point-by-point basis, a number
of spectra or interferograms. Coaddition is used to increase the signal-tonoise
ratio of a spectrum.
desiccant
A substance used as a drying agent.
detector
A device in a spectrometer that produces an electrical signal that is
proportional to the intensity of the light striking it.
detector cut-off
The frequency or wavelength at lower end of the spectral range.
detector saturation
A condition of the detector whereby an increase in the light intensity
striking it no longer produces a linearly proportional change in the output
signal. This is a nonlinear condition and can cause Fourier stray light.
D-star (D*)
A value used to designate the specific detectivity. This is a performance
measure independent of detector size. The higher is the D* value, the better
is the detector.
1
2
D*
= (A × ∆f ) D
where A is the sensitive area
∆f is the bandwidth frequencies
D is the reciprocal of noise equivalent power (NEP)
factor
In analysis using the PLS algorithm, one of a series of synthetic spectra
which represent the most common variations in a given set of spectra
(also known as latent vectors, characteristic vectors, spectral loadings,
loading vectors, principal components, or variation spectra.).
50 Bomem-GRAMS User's Guide