Color shift of head lamps for automotive lighting over lifetime

The color shift of head lamps for automotive lighting over lifetime was investigated. For that purpose a combination of emission spectroscopy and thermography was used to determine spectra, color data and the cold-spot temperature. There are changes in the lamp behavior over lifetime with a visible blue shift until 500 h and a reversal afterwards. The cold-spot temperature is nearly constant until 1000 h and then increases slowly. The different behavior of Sc und Na partial pressure with increasing lifetime leads to a change of the spectral output of the lamp and therefore of the color appearance over lifetime