LumaSense Technologies MCS640 Manual - Manual (Page 18)

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Section 4 Principles of Thermal Imaging
Where in (1) to (3),
In radiation of a normal object, as the emissivity is (<1) times of the blackbody, multiply
above equation by the emissivity. The following figures show the spectral radiant
emittance of a blackbody.
(a) is shown by logarithmic scale and (b) is shown by linear scale.
The graphs show that wavelength and spectral radiant emittance vary with the
temperature. They also show that as the temperature rises, the peak of spectral radiant
emittance is shifting to shorter wavelengths. This phenomenon is observable in the
visible light region as an object at a low temperature appears red, and as the temperature
increases, it changes to yellowish and then whitish color—thus shifting to shorter &
shorter wavelengths as the temperature increases.
4.4 Blackbody Type Source and Emissivity
Although a blackbody is actually only a theoretical ideal, an object can be manufactured
which approximates it. A law closely related to the blackbody is Kirchhoff’s law that
defines reflection, transmission, absorption and radiation.A
a = e = 1
spectral radiant emittance of a
blackbody
Key:
a = absorptivity
t = transmissivity
r = reflectivity
e = emissivity