INFRARED THERMOGRAPHY : PRINCIPLES AND APPLICATIONS

Summary All objects with surface temperatures above absolute zero emit electromagnetic radiation. In this paper we de­scribe the physical principles that allow calculation of the surface temperatures of objects from the wavelength and intensity of electromagnetic radiation emitted in the in­frared region of the spectrum (infrared thermography). This technique can be applied to measure the surface temperature of animals without the need for physical con­tact with them. Infrared thermography allows a direct measure of radiative heat transfer from animals. Convec­tive heat transfer can also be calculated from the detailed information on body surface temperature. We describe some recent applications of infrared thermography to re­mote measurement of surface temperature which allow identification of the main sites of heat loss from mammals and birds. Introduction Ail objects that have surface temperatures above absolute zero emit electromagnetic radiation. This radiation can be characterised by two features; its wavelength Ck) and intensity (0). Both of these pa­rameters are related by relatively simple physical laws to the surface temperature of the object (Hol­man 1-986). It is therefore possible to use the inten­sity and wavelength of radiation emitted by an ob­ject to measure its surface temperature, without the need for physical contact. This allows the study heat transfer from animals in situations where con­ventional measurements using thermistors could not be used (for example during flight: Lancaster et at 1997, Speakman et af 1997).

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