Jenoptik VARIOSCAN high resolution Series Manual page 53

Temperature measurement
interpolation from the deviation of the calibration points from the ideal
Planck black body radiator curve. This method guarantees that the
temperature scale of the camera exactly coincides with all calibration
points and that the interpolated values follow the Planck black body
radiator curve in the first approximation.
Beside different internal parameters, the formulas implemented in the
control software take into account the following quantities that are either
entered by the user, automatically detected by the camera or loaded as
constants:
q Emission and distance of measured object
q Atmospheric transmission and temperature
q Emission and temperature of ambient objects
q Emission and temperature of the reference radiator
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