Fourier Transform Infrared System Measurement of the Bidirectional Reflectivity of Diffuse and Grooved Surfaces

Abstract

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.

Accurate determination of the total hemispherical emittance and solar absorptance of opaque surfaces at elevated temperatures

“…However, this already leads to one of the main shortcomings of these techniques when used for low-emittance samples because a small relative error in the measured reflectance results inevitably in a significantly larger relative error in emittance [9]. Nevertheless, there are various absolute and relative techniques used to measure the spectral bidirectional, spectral directional-hemispherical or spectral hemispherical-directional reflectance using monochromatic or polychromatic light sources [2,7,[10][11][12][13][14][15]. Here, we use the term "spectral" to refer to the reflectance or emittance at a single wavelength, as opposed to the term "total" which refers to the property averaged over a given spectrum (e.g.…”

Scatterometer of visible light for 2D rough surfaces

“…[6][7][8][9] These devices are useful for one-dimensional and bidimensional surfaces, and reduce the time needed to study the surface. Nevertheless, most of them only work in the near infrared region of the spectrum because in that region the aberrations are smaller compared to the wavelength and, in consequence, they have a smaller effect on the image.…”