The dependence of the spectrometer scanning function on the spatial coherence of the illumination at the entrance slit implies that the spatial coherence of laser radiation must be degraded before its narrow spectral bandwith can be used to advantage in scanning-function calibration. A conventional incoherent source can be simulated by using a source having a relatively large correlation interval, provided that its correlation function has a favorable form. Partial-coherence theory is used to obtain conditions on the correlation function resulting from the properties of Globar radiation. The correlation function at a spectrometer entrance slit is experimentally determined using a method described by Beran and Parrent. The results for an incoherent Hg source are in agreement with Hopkins's concept of an effective source. Results using laser light reflected from an integrating sphere indicate that such a source may be used interchangeably with an ordinary incoherent source for scanning-function calibration.
LOUIS SICA, "Use of Laser Radiation in the Calibration of Spectrometer Scanning Functions," J. Opt. Soc. Am. 57, 1366-1371 (1967)