We have developed a goniometric reflectometer using a Fourier-transform infrared (FTIR) spectrometer source for polarized reflectance measurements from 1 um to 20 um wavelength at angles of incidence from 10° to 80°, with an incident beam geometry of approximately f/25. Measurements are performed in either absolute mode, or relative to a reference mirror that has been calibrated at near-normal incidence using an integrating sphere-based reflectometer. Uncertainties in the 0.2 % to 0.5 % range are achieved using a photoconductive 77 K InSb detector from 1 um to 5 um and a 12 K Si:As BIB detector from 2 um to 20 um. The performance of the system has been tested using dielectric materials such as Si as well as high-quality Au mirrors. We describe measurements of SiOx-coated Ag mirrors similar to the half-angle mirror (HAM) used in the VIIRS optical scanning system. Various coatings are analyzed to help assess the effect of p-polarized absorption bands at angles from 10° to 65° and wavelengths between 3 um and 13 um.
Proceedings Title: SPIE Infrared Spaceborne Remote Sensing and Instrumentation XVI
Conference Dates: August 10-14, 2008
Conference Location: San Diego, CA
Pub Type: Conferences
infrared, optical coatings, polarization, radiometry, reflectance