New calibration method for prism infrared spectrometers

Based on the minimum deviation equation N sinø = sin(ø + ø), a linear equation which relates drum screw scale to arcsin(N sinø) for the prism spectrometer calibration has been developed. The use of this linear equation and the dispersion formula for prism material allows the preparation of a calibration table of numbers, rather than the usual less precise drum-wavelength calibration curve, for practical transfer of wavelength drum-scale values D to wavelengths lambda. The method requires only two or three reference points, applicable to various prisms with high accuracy in their recommended wavelength range. The linearity suggests another advantage, because it permits linear transformation of the old drum setting for a prism that was first calibrated to the new drum setting.