SpectralEmissivity & Emittance

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ET10 Reflectometer Measures Emissivity

San Diego CA, USA –Surface Optics’ ET10 measures emissivity values in two most commonly used spectral regions, 3 to 5 and 8 to 12 microns.

Its main application is to produce emissivity values for the infrared cameras.

Advanced IR cameras require the input of an emissivity value for accurate temperature calculations. The emissivity values obtained from tables can be far from real leading to large temperature uncertainties.

The ET10 can be used in the lab or in the field and on small or large objects. With the ET10 one can measure emissivity of any surface in just a few seconds.

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Infrared Emission Spectroscopy of Polymer Reactions

Noninvasive Polymer Reaction Monitoring by Infrared Emission Spectroscopy with Multivariate Statistical Modeling
Randy J. Pell, James B. Callis, and Bruce R. Kowalski
Applied Spectroscopy, Vol. 45, Issue 5, pp. 808-818 (1991)

Abstract

“Infrared absorption and emission spectroscopy have been used to monitor the curing of a commercial paint product. Principal component analysis of the absorption data indicates that three factors are needed to explain the observed spectral/temporal variance. The interpretation of this finding in terms of changes in the physical state of the reaction mixture is discussed. A similar analysis of the emission data proved more difficult due to a nonlinear concentration/response relationship. A linearization step based on an approximate theoretical model is suggested. The absorption, linearized emittance, and raw emittance data are fit to a two-step sequential rate model using multivariate nonlinear optimization and error estimates derived by Monte Carlo calculations. Better agreement of the model parameters between the absorbance and emittance data is found after linearization, but it is found that linearization introduces large errors in the nonlinear parameter estimates. Comparisons of model parameters for the raw emittance data at different temperatures are made.”

Citation
R. J. Pell, J. B. Callis, and B. R. Kowalski, “Noninvasive Polymer Reaction Monitoring by Infrared Emission Spectroscopy with Multivariate Statistical Modeling,” Appl. Spectrosc. 45, 808-818 (1991)

Spectral Reflectivity of Epner Laser Gold

Courtesy of Epner Technology, Inc.

(CLICK ON GRAPH TO ENLARGE)
Almost everyone who attends the SPIE DSS Exposition and many other optical and optical engineering Conferences & Expos has received a gold-plated paper clip from Mr. David Epner, personally.

Well, the gold costing that Epner supplies to the optics industry has some interesting infrared reflectance (and emittance) properties.

Those properties, specifically the hemispherical spectral reflectance in the near, mid and far infrared is now available for all to view first hand on the Epner website.

A copy of the curve and the data related to it can be downloaded from the site, too.

Shown here, of course, is the Spectral Reflectance of “Laser Gold”, which as most know is the complement of Spectral Emittance at each and every wavelength from the formula: e(lambda) = 1 – r(lambda) – t(lambda),

where, respectively:

e is the emittance,
r is the reflectance,
t is the transmittance and
lambda is the wavelength (on this graph shown in units of micrometers). (Note: the usual expressions for these terms are in the Greek letters, epsilon, rho, tau and lambda and have been modified for use on this webpage)

The assumption most often made is that the transmittance of solid gold is zero, or so nearly so that it can be neglected.

That can be an false assumption in some cases according to the degree of precision required in a specific measurement situation. For instance, a very thin film of gold may be partially transparent especially in the long wavelength regions of the infrared and the optical properties on the material under the gold layer may come into play.Read More