Lumasense-technologies MCS640 Manual Bedienungsanleitung PDF herunterladen (Seite 18)

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 gures 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

denes reection, transmission, absorption and radiation.A

a = e = 1

Spectral radiant emittance of a

blackbody

Key:

a = absorptivity

t = transmissivity

r = reectivity

e = emissivity

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Lumasense-technologies MCS640 Manual Bedienungsanleitung Seite 18