LumaSense Technologies MC320 Manual - Manual (Page 22)

22 Principle of Thermal Imaging MC320 Thermal Imager Manual
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.
Spectral radiant
emittance of a
blackbody
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 and
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 = e = 1
Key:
a = absorptivity
t = transmissivity
r = reflectivity
e = emissivity