Fourier transform infrared system measurement of the bidirectional reflectivity of diffuse and grooved surfaces

A system based on a Fourier transform infrared spectrometer is developed to perform bidirectional reflectivity measurements on material surfaces, providing the ability to measure this property simultaneously for multiple infrared wavelengths. Calibration is based on a relative method that relates the system output to absolute spectral bidirectional reflectivity. Results are presented for rough gold and grooved nickel surfaces, considering the variation with incident and reflected angle. The surface reflectivity for gold is largely independent of wavelength in the infrared region of interest, while the nickel surface exhibits spectral variation. The experimental results are compared to complete electromagnetic theory predictions and other measurements.