Proceedings Article | 29 August 2008
Proc. SPIE. 7065, Reflection, Scattering, and Diffraction from Surfaces
KEYWORDS: Mirrors, FT-IR spectroscopy, Data modeling, Sensors, Reflectivity, Reflectometry, High dynamic range imaging, Aluminum, Signal detection, Temperature metrology
We have developed a system to measure the directional thermal emission from a surface, and in turn, calculate its
emissivity. This approach avoids inaccuracies sometimes encountered with the traditional method for calculating
emissivity, which relies upon subtracting the measured total reflectivity and total transmissivity from unity. Typical total
reflectivity measurements suffer from an inability to detect backscattered light, and may not be accurate for high angles
of incidence.
Our design allows us to vary the measurement angle (θ) from near-normal to ~80°, and can accommodate samples as
small as 7 mm on a side by controlling the sample interrogation area. The sample mount is open-backed to eliminate
shine-through, can be heated up to 200 °C, and is kept under vacuum to avoid oxidizing the sample. A cold shield
reduces the background noise and stray signals reflected off the sample. We describe the strengths, weaknesses, trade-offs,
and limitations of our system design, data analysis methods, the measurement process, and present the results of our
validation of this Variable-Angle Directional Emissometer.
