Further development of an LED-based radiation source for goniometric spectral radiance factor measurements

In previous work, the suitability of LEDs as a radiation source for the gonioreflectometer was investigated. An LED-Sphere Radiator (LED-SR) was constructed and its essential properties were described [1]. Based on these investigations, the further development of the LED-SR is presented here. Significant improvements such as a specially developed high-power LED board and active temperature control have been made. Due to the great influence of the reflecting insert on the radiation characteristics of the sphere, its optical and mechanical properties have also been optimized. Investigations with respect to these modifications and their effects are explained. The achieved improvements and the performance of the LED-SR are evaluated in comparison to measurements with the typically used halogen sphere radiator (Halogen-SR). It can be shown that with the new radiator more accurate results can be obtained in the observed spectral range in a shorter measurement time.