Construction and characterization of a high luminance level source based on high power multi-chip white LEDs

In order to calibrate the luminance measurement devices at higher luminance ranges, a luminous source with a high-level light output is required. Such sources are usually provided by halogen lamps. However, with the developing semiconductor technologies in recent years, the creation of light sources with high-power white light-emitting diodes (LEDs) has begun to be included in the field of metrology. For this reason, a luminous source having a wide range of luminance production capabilities has been developed. The source was based on an integrating sphere with two high-power white LEDs and a variable power supply. Forced convection was utilized by using a cooling fan to increase the heat transfer together with the existing heat sink to prevent the LEDs from being damaged at high current levels and to provide stable optical output. The cooling performance of the LEDs and optical characterization studies such as the spectral characteristics and produced luminance depend on driving currents and spatial surface homogeneity of the constructed luminance source were also carried out. With the constructed luminance source, luminance calibration of a meter up to 200000 cd/m2 level can be performed.