Emissivity of Human Skin in the Waveband between 2 & 6 micrometers

From a Nature Article of the same title:

By DAVID J. WATMOUGH & R. OLIVER, Department of Radiation Physics, Churchill Hospital, Oxford.
Citation: Nature 219, 622 - 624 (10 August 1968); doi:10.1038

Abstract:

The emissivity of human skin epsilon(lambda) in the range 2micro to 6micro has recently assumed considerable importance because of the increasing medical use of infrared scanners to measure skin temperature (t). Several commercially available scanners utilize indium antimonide detectors which are sensitive in the range 2micro to 5.4micro . Such machines measure the energy (Q) Bactrim radiated by the skin and, being calibrated against a standard black body, changes in Q are represented as variations in skin temperature. Dreyfus1 has shown that Q is related to t by an equation of the form, where k is a constant, and where the index n depends on lambda as lambdamax being the wavelength corresponding to the maximum in the emission curve. The importance of variations in emissivity can be seen by differentiating equation (1) for constant Q. We obtain which simplifies to give for Deltat For a skin temperature of 27° C (t=300° K), n is about 12.5. It follows from equation (2) that if epsilon(lambda) were to vary by as much as 5 per cent over the skin surface, this would be interpreted by the scanner as a temperature variation of about 1° C. A fairly accurate knowledge of epsilon(lambda) is thus necessary, for hot spots with temperature elevations of only 2° C are considered to be of clinical significance.

Determination of the Infrared Emissivity with Multi-spectral Thermal Infrared Data from Space

A 2004 Amercian Geophysical Union Conference Presentation by:


Schmugge, T (schmugge@hydrolab.arsusda.gov) , USDA/ARS Hydrology and Remote Sensing Lab, Bldg. 007 - BARC West, Beltsville, MD 20705 United States
Ogawa, K (k-ogawa@dsg.hitachi.co.jp) , Hitachi Ltd., 4-6 Kanda-Surugadai Chiyoda- Ku,, Tokyo, 101-8010 Japan
Ogawa, K (k-ogawa@dsg.hitachi.co.jp) , Faculty of Engineering,University of Tokyo, University of Tokyo, Tokyo, 113-0033 Japan
Rokugawa, S (rokugawa@gpl.t.u-tokyo.ac.jp) , Faculty of Engineering,University of Tokyo, University of Tokyo, Tokyo, 113-0033 Japan

Fluke Calibrator Video

Emissivity makes a temperature difference for infrared thermometers.

In the YouTube video below, Frank Liebman, an engineer with Fluke Corporation's Hart Scientific Division demonstrates the impact that surface emissivity has on temperature measurement and temperature calibration using a modified Fluke blackbody calibrator and Fluke Thermal Imager.



We were surprised to see that no one commented on this video, despite an ending that leaves one hanging, at least us, with the obvious question: How do you do a radiometric calibration of a surface of unknown emissivity using a Fluke Blackbody Calibrator?

Do you have any ideas?

What The Heck is Emissivity? (Part 2)

Fill up two soda cans with hot water and wrap one in scotch tape. Which one will cool down faster? Obvious, right?

Check it out, you might be surprised!

From the ITC Channel at YouTube.com

Measurement of the surface emissivity of turbid waters

Chinese Journal of Oceanology and Limnology, Volume 5, Number 4, 363-369, DOI: 10.1007/BF02843818

"Measurement of the surface emissivity of turbid waters", Liu Wenyao, R. T. Field, R. G. Gantt and V. Klemas

http://www.springerlink.com/content/8102732046620458/

Abstract
For interpreting thermal IR imagery of the ocean surface, the emissivity of the sea surface is usually assumed to be constant, approximately 0.98. However, the emissivity varies with the roughness of the sea surface, and the concentration and type of suspended particulates.

The emissivity variations caused by the suspended sediments introduce significant errors in the satellite-derived temperature maps of turbid coastal waters.

IR contrast of crude-oil-covered water

"Infrared contrast of crude-oil-covered water surfaces", by Wei-Chuan Shih and A. Ballard Andrews, Optics Letters, Vol. 33, Issue 24, pp. 3019-3021 (2008)

Abstract (Modified format for easier online viewing)

Emissivity of thin oil films

Unpolarized emissivity of thin oil films over anisotropic Gaussian seas in infrared window regions,"

Appl. Opt. 49, 2116-2131 (2010), by Nicolas Pinel, Christophe Bourlier, and Irina Sergievskaya is online at:
http://www.opticsinfobase.org/abstract.cfm?URI=ao-49-11-2116.

Abstract (Modified format for easier online viewing)

Thermal infrared remote sensing of crude oil slicks

In: Remote Sensing of Environment, Volume 45, Issue 2, August 1993, Pages 225-231.

by John W. Salisbury ^a, Dana M. D'Aria ^a and Floyd F. Sabins Jr.^b
aDepartment of Earth and Planetary Sciences, Johns Hopkins University, Baltimore U.S.A.
^bChevron Oil Field Research Company, La Habra, California U.S.A.

(Abstract Online)
With all the interest on the Gulf Oil spill and recent accounts of the use by British Petroleum and others of Infrared Thermal Imaging to search for surface oil slicks, it seemed very timely to be sure we had included some links and summaries of articles dealing with the thermal Infrared optical properties of crude oil on seawater.

Article Abstract

Emissivity of human skin

Novel approach to assess the emissivity of the human skin
J. Biomed. Opt., Vol. 14, 024006 (2009); DOI:10.1117/1.3086612 Published 6 March 2009
by: Francisco J. Sanchez-Marin, Sergio Calixto-Carrera, and Carlos Villaseñor-Mora
Centro de investigaciones en optica, Loma del Bosque 115, Lomas del Campestre, Leon, Guanajuato 37150, Mexico

Abstract:

To study the radiation emitted by the human skin, the emissivity of its surface must be known. We present a new approach to measure the emissivity of the human skin in vivo. Our method is based on the calculation of the difference of two infrared images: one acquired before projecting a CO2 laser beam on the surface of the skin and the other after such projection. The difference image contains the radiation reflected by the skin, which is used to calculate the emissivity, making use of Kirchhoff's law and the Helmholtz reciprocity relation. With our method, noncontact measurements are achieved, and the determination of the skin temperature is not needed, which has been an inconvenience for other methods. We show that it is possible to make determinations of the emissivity at specific wavelengths. Last, our results confirm that the human skin obeys Lambert's law of diffuse reflection and that it behaves almost like a blackbody at a wavelength of 10.6 µm.

Editor's Note: Back in the 1960s there were several serious projects mounted by the US Army Medical Research Laboratory's BioPhysics Division on determining injury thresholds of laser radiation on human skin analogs. The article "THRESHOLD LESIONS INDUCED IN PORCINE SKIN BY CO2 LASER RADIATION" by Brownell, Arnold S. ; Parr, Wordie H. ; Hysell, David K. ; Dedrick, Robert, USAMRL Report No. 7327, June 1967, is available as a pdf download at: http://handle.dtic.mil/100.2/AD659347.

Although not fully described in the article, the measured results compared favorably with a semi-infinite solid model of heat conduction for a surface that was essentially black (10.6 micron spectral absorptivity or emissivity very close to 1.0) or fully absorbing at 10.6 microns. This editor was a member of the USAMRL BioPhysics Division staff at that time and helped with the dosimetry of the experiments described.

What the Heck is (Spectral) Emissivity?

Part One of Two from the mind of FLIR
It health partners pharmacies starts:

Fill two soda cans with hot water and wrap one with scotch tape. Which one will radiate more heat?

You might be surprised at the answer

(It has all to do with Spectral Emissivity, although this video continues the illusion that it's really simple "Emissivity" at work! The concept of Emissivity is simple and easy to grasp as the video shows. The understanding is a bit more difficult and begins when one realizes that it is really Spectral Emissivity.)

But looking beyond that technical fine point, the video illustrates two other things: