Advances in multilayer interference filter technology have enabled the development of filter grating spectrophotometers out to 250 cm−1 (40 μ). Properties of the filters are described. Factors which determine the rejection and transmission requirements for the filters are discussed and special design problems in filter grating systems are elaborated. Unwanted radiation measurements in the resulting system are reported. The features of filter grating spectrophotometers compared to foreprism grating instruments are listed.
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