We have performed transmittance measurements of metal-film neutral density filters on ultrathin polymer substrates using both Fourier-transform infrared spectrometer and laser-based (3.39 mm and 10.6 mm) systems. The use of ultrathin substrates, free of etaloning effects over the 2 mm to 20 mm spectral range, allows the FT-IR and laser measurements to be directly compared. We discuss the evaluation of the uncertainties in the transmittance values in both types of systems.
Citation: SPIE series
Pub Type: Journals
infrared, neutral-density filter, transmittance