Varioilluminator (subtractive double monochromator with variable bandpass).
A varioilluminator is a double monochromator in which the dispersion in the second half of the instrument is subtractive rather than additive and in which the central slit can be opened very wide. The wavelength bandpass depends almost entirely upon the width of the central slit. The jaws of the central slit in the instrument described here were made independently variable, so that the long and short wavelength cutoffs could be independently selected. Quartz or glass prisms could be used, and bandpasses from about 15A to several hundred Acould be chosen.
Lipsett
F R
FR
Oblinsky
G
G
Johnson
S
S