stated above spectral resolution expresses the ability, for an optical
system, to resolve near lines, for example an analytical line and a
line of the matrix. To carry out an analysis without the need for
numerous inter-element corrections, adequate resolution is necessary,
hence a grating with a large number of lines.
resolution can be improved by reducing the width of the spectral slits,
but signal strength (luminosity) is also reduced.
given grating and in a given order, the spectral resolving power is
proportional to the focal length of the optical system and to the
reciprocal of the entrance and exit slit widths. It is exactly the
opposite for system brightness.
achieve the resolution necessary for analyses, one can increase either
the focal length of the system for a given grating, or the number of
lines of the grating for a given focal length.
when the system's focal length is increased, its mechanical stability
may be impaired and, for the same grating, brightness is reduced.
Stability is a critical characteristic for equipment which must retain
its calibration characteristics over a long period of time. Further,
brightness is invaluable as it is synonymous with good detection limits
Author: Jean Charles Lefebvre, Horiba Jobin-Yvon
First published on the web: 15 November 1999.