Reflection and transmission measurements with an integrating sphere and Fourier-transform infrared spectrometer.

A method of measuring the total reflection and transmission spectra of scattering materials with an integrating sphere and a Fourier-transform infrared spectrometer is studied. The reflectance measurement system is considered in a specific case where the incident beam overfills the back side port of the sphere, and the correction functions for measured spectra are derived for this case. Correction formulas are based on the energy balance between incident radiation and absorbed or escaped radiation in the system. The absorption spectrum of the material is calculated from the corrected spectra. The optical properties of paper samples and radiating surfaces of infrared dryers in the 0.4-20-microm wavelength range are determined. The correction formulas are compared with previous work presented in the literature.