Diffraction Losses Associated with Tungsten Lamps in in Absolute Radiometry

The diffraction losses associated with absolute radiometers were calculated for the case where the source is a tungsten lamp used with a long wavelength suppressing filter. The calculations were done using Blevin's treatment, which assumes a point source and a single diffracting aperture. We have shown that this treatment is sufficiently accurate for a typical absolute radiometer configuration. The calculations were done for color temperatures in the 1600-3200 K range for three typical glass filters.