Spectral Emissivity & Emittance

Emittance measurements on infrared windows exhibiting wavelength dependent diffuse transmittance
S. E. Hatch
Applied Optics, Vol. 1, Issue 5, pp. 595-601

Citation
S. E. Hatch, “Emittance measurements on infrared windows exhibiting wavelength dependent diffuse transmittance,” Appl. Opt. 1, 595-601 (1962)

Spectral emittance of refractory materials
Henry H. Blau, Jr. and John R. Jasperse
Applied Optics, Vol. 3, Issue 2, pp. 281-(1964)

Citation
H. H. Blau, Jr. and J. R. Jasperse, “Spectral emittance of refractory materials,” Appl. Opt. 3, 281- (1964)

Infrared spectral emittance measurements of optical materials
D. L. Stierwalt
Applied Optics, Vol. 5, Issue 12, pp. 1911-(1966)

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Citation
D. L. Stierwalt, “Infrared spectral emittance measurements of optical materials,” Appl. Opt. 5, 1911- (1966)

Ircon, Inc., a leading producer of industrial radiation thermometers, line scanners and quantitative thermal imagers, in its training programs for many years used to teach something they called the RAT Theory.

Reflectance, Absorbtance and Transmittance, or the coefficients of them, abbreviated as R, A &T must sum to 100%, or R + A + T=1.

An easy way for newcomers to Infrared radiation thermometry to remember a very important concept.

The associated concept is that Absorbtance=Emittance, or A=E. Or the RAT theory could be written as R+E+T=1 and renamed the RET Theory.

So, while not as easily recalled, the RET Theory name just didn’t catch on as easily as the RAT Theory.

(BTW, whenever I tried to teach some basics of Radiation Thermometry, I used to call it the TAR Theory because I thought it might “stick” better- it didn’t - RAT wins by a landslide every time.)

Al this is a lead in to the wonderful resources by the folks at  LabSphere for those who want to know or learn how to measure emittance or absorbtance through the roundabout way of measuring reflectance and transmittance first and then doing a bit of math.

They have a readily downloadable 26 page PDF document entitled “A Guide to Integrating Sphere Radiometry and Photometry”.

It explains far more than the RAT or RET or TAR theories about optical radiation metrology.

I think it and many of their online aids are well worth a read.

Spectral emittance and reflectance of powders
J. R. Aronson, A. G. Emslie, T. P. Rooney, I. Coleman, and G. Horlick
Applied Optics, Vol. 8, Issue 8, pp. 1639- (1969)

Citation
J. R. Aronson, A. G. Emslie, T. P. Rooney, I. Coleman, and G. Horlick, “Spectral emittance and reflectance of powders,” Appl. Opt. 8, 1639- (1969)

Cavity methods for determining the emittance of solids
E. M. Sparrow, P. D. Kruger, and R. P. Heinisch

Applied Optics, Vol. 12, Issue 10, pp. 2466- (1973)

Citation
E. M. Sparrow, P. D. Kruger, and R. P. Heinisch, “Cavity methods for determining the emittance of solids,” Appl. Opt. 12, 2466- (1973)

Spectral reflectance and emittance of particulate materials
A. G. Emslie and J. R. Aronson
Applied Optics, Vol. 12, Issue 11, pp. 2563-

Citation
A. G. Emslie and J. R. Aronson, “Spectral reflectance and emittance of particulate materials,” Appl. Opt. 12, 2563- (1973)

Spectral emissivity of hydrogen chloride from 1000-3400 cm-1 V
V. Robert Stull and Gilbert N. Plass
JOSA, Vol. 50, Issue 12, pp. 1279- (1960)

Citation
V. R. Stull and G. N. Plass, “Spectral emissivity of hydrogen chloride from 1000-3400 cm-1 V,” J. Opt. Soc. Am. 50, 1279- (1960)

Authors: Madding, Robert P.\
Affiliation: AA(Inframetrics, Inc.)
Publication:
Proc. SPIE Vol. 3700, p. 393-401, Thermosense XXI, Dennis H. LeMieux; John R. Snell; Eds. (SPIE Homepage)
Publication Date:03/1999
Origin:SPIEAbstract Copyright:
(c) 1999 SPIE–The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Bibliographic Code: 1999SPIE.3700..393M
Abstract: Extraction of temperatures or temperature differences with thermography is not possible without knowledge of the target emissivity…

A project under the Tufts University Research for Undergraduates 2000 Program described both theory and experiments related to welding of metals. Its report is online (CLICK HERE FOR FULL REPORT) and the Abstract is below.

Abstract

“The basic assumption behind the operating principle of modern thermal imaging thermometers is a “graybody approximation”. For a graybody, the emittance, reflectance and transmittance are constant for all wavelengths within the wavelengths within the waveband over which the instrument measures.

“In reality however, these factors change, and for applications that take place over a wide temperature range, the emissivity variation needs to be taken into account. This work suggests a method for an in-process emissivity identification and adaptation in order to dynamically calibrate infrared temperature measurement systems for applications like heat treatment, welding, cutting etc. A series of experiments has proven that once the spatial and temporal components of emissivity are decoupled, a model can be developed, which in conjunction with direct IR radiosity monitoring can provide information about the required emissivity compensation.”