MCS640 Thermal Imager Manual
Principle of Thermal Imaging
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Principle of Thermal Imaging
All materials above 0 degrees Kelvin (-273 degrees C) emit infrared energy. The infrared energy emitted from
the measured object is converted into an electrical signal by the imaging sensor in the camera and displayed
on a monitor as a color or monochrome thermal image. The basic principle is explained in the following
sections.
4.1
Infrared Radiation
The infrared ray is a form of electromagnetic radiation the same as radio waves, microwaves, ultraviolet rays,
visible light, X-rays, and gamma rays. All these forms, which collectively make up the electromagnetic
spectrum, are similar in that they emit energy in the form of electromagnetic waves traveling at the speed of
light. The major difference between each ‘band’ in the spectrum is in their wavelength, which correlates to the
amount of energy the waves carry. For example, while gamma rays have wavelengths millions of times smaller
than those of visible light, radio waves have wavelengths that are billions of times longer than those of visible
light.
A Spectrum of Electromagnetic Radiation
The wavelength of the infrared radiation ‘band’ is 0.78 to 1000 µm (micrometers). This is longer than the
wavelength of visible light yet shorter that radio waves. The wavelengths of infrared radiation are classified
from the near infrared to the far infrared.
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 reflect 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.
