Lumasense-technologies MCS640 Manual Manual de usuario descargar pdf (Pagina 16)

Section 4 Principles of Thermal Imaging

4.2 Emissivity

Infrared radiation is energy radiated by the motion of atoms and molecules on the surface

of object, where the temperature of the object is more than absolute zero. The intensity

of the emittance is a function of the temperature of the material. In other words, the

higher the temperature, the greater the intensity of infrared energy that is emitted. As

well as emitting infrared energy, materials also reect infrared, absorb infrared and, in

some cases, transmit infrared. When the temperature of the material equals that of its

surroundings, the amount of thermal radiation absorbed by the object equals the amount

emitted by the object.

The gure above shows the three modes by which the radiant energy striking an object

may be dissipated. These modes of dissipation are:

a = absorption

t = transmission

r = reection

The fractions of the total radiant energy, which are associated with each of the above

modes of dissipation, are referred to as the absorptivity (a) transmissivity (t) and the

reectivity (r) of the body. According to the theory of conservation of energy, the extent

to which materials reect, absorb and transmit IR energy is known as the emissivity of

the material.

Transmission, Absorption, and

Reﬂection of Infrared Energy

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Lumasense-technologies MCS640 Manual Manual de usuario Pagina 16