Measurement of the radiated power is a key step in the thermal characterization of
power LEDs. However, as the LEDs age, the light transmittance of the lens may decrease,
which blurs the results of the thermal measurements. The combined thermal and radiometric
characterization techniques of power LEDs does not take into account any aging effect
of the LEDs, while the most widely accepted lifetime testing procedures seem to ignore
the thermal aspects. Consequently, the results of measurements performed blindly in
accordance with the standards will be ambiguous and the operator performing the measurement
will not even be aware of this fact.
