Dynamic Optical Power Measurements and Modeling of Light-Emitting Diodes Based on a Photodetector System and Photo-Electro-Thermal Theory

Optical measurements based on integrating sphere are primary suitable for steady-state measurements and unsuitable for dynamic real-time measurements. This paper presents an alternative method using the combination of a photodetector system and the dynamic photo-electro-thermal theory for real-time optical measurements. It is demonstrated that the voltage output of a photodetector can be correlated to the optical power in real time. Such method has been successfully applied to analyze a phosphor-converted white light-emitting diode (PC white LED) using an extended dynamic model with separate calculations of optical power from the blue LED chips and phosphor layer. Both calculated and practical results are included to confirm the validity of the new method.