A Design for In-Situ Measurement of Optical Degradation of High Power Light-Emitting Diodes Under Accelerated Life Test

To better understand the reliability problem in high-power light-emitting diodes (LEDs), an online test is critical under an accelerated life test. In this paper, an experimental equipment was proposed for in situ measurement to evaluate the degradation of LED´s optical properties. Signals such as illuminance and correlated color temperature were transmitted by the heat-resistant optical cable and were finally collected by detectors with high precision. The multichannel outputs were provided to simultaneously measure several samples. The measuring distance optimization was conducted by a ray tracing method, and the characteristics of optical output were listed. Accelerated life tests also indicate that the system error is less than 0.2%, and the measuring uncertainty of equipment can be controlled within 2%. A comparison experiment according to LM-80 measurement standard also shows a good agreement between the experimental data and the reference value.