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Description / Abstract:
This report describes the effect of instrumental bandpass and
measurement wavelength interval on spectral quantities and provides
recommendations on suitable methods to minimize the effect of
instrumental bandpass functions. The report concentrates on a
correction method of the form commonly used, that of a weighted
mean over surrounding values applied to the data and based on
assumption of the form of the spectrum across the bandpass. The
report also provides information relating to the determination of
the bandpass function itself for both monochromators and
spectrometers.
As this report was being compiled, a true deconvolution method,
not dependent on assumptions about the spectrum, was being
developed (Eichstaedt et al. 2013). This method offers the promise
of better spectral correction than the weighted-mean methods
described in this report, but further study is required and a
detailed description is not included here. Weighted-mean methods
are simple to apply and give good results for spectral integrals
(e.g. as in colorimetry), which are a common application of
bandpass correction.
This report also describes the effect of instrumental bandpass
on spectrally integrated quantities, but it does not cover the
propagation of errors and uncertainty from spectral measurement to
spectrally integrated quantities.
Other related effects in spectrometer characterization include
stray-light correction and wavelength accuracy. These are included
only in as far as they affect the determination of the bandpass
function. Full determination and correction of stray-light and
wavelength errors are not described within this report.