A Fourier-transform infrared (FT-IR) spectrophotometer system is used to measure the transmittance of infrared band-pass filters as a function of wavelength, temperature, and beam geometry. Measurements are performed using an f/4 beam geometry at normal incidence, or a nearly collimated geometry with variable angle of incidence. Blocking filters are used to expand the dynamic range of the out-of-band measurement to transmittances as low as 10-6 with 4 cm-1 resolution.
Citation: SPIE series
Pub Type: Journals
filter, infrared, transmittance