COMPARISON OF EMISSIVITY MEASUREMENTS USING ANINTEGRATING SPHERE REFLECTOMETER AND A LASER POLARIMETERON SURFACES WITH VARIOUS DEGREES OF ROUGHNESS

摘要

Laser polarimetry has been used for years toobtain normal spectral emissivity measurements on pulseheatedmaterials [1, 2]. The method is based on theFRESNEL equations that describe reflection and refractionat an ideally smooth interface between two isotropic media.However, polarimetry is frequently used with surfaces thatclearly deviate from this ideal condition. Questions arisewith respect to the applicability of the simple FRESNELequations to non-specularly reflecting surfaces. On the otherhand, reflectometry utilizing integrating spheres provides ameasurement of the hemispherical spectral reflectance fornormal incidence, from which the normal spectralemissivity1 can be derived, regardless of surface texture. In afirst effort to explore the limits of polarimetry in terms ofsurface roughness, room temperature measurements wereperformed on a number of samples using both an integratingsphere reflectometer and a laser polarimeter. In this paper,the two methods are briefly described and the results of thecomparison are discussed.