Determining Two-Dimensional Phosphor Surface Temperature Distribution of Phosphor-Coated LEDs Based on Hyper-Spectral Imaging

We present a high-resolution non-contact method for the measurement of two-dimensional (2D) phosphor surface temperature distribution (PSTD) of phosphor-coated light-emitting diodes (pc-LEDs) based on advanced hyper-spectral imaging technology. The studied pc-LEDs with a surface-mounted device structure are mainly consisted of blue InGaN/GaN-based LED chips (with a spectral emission at about 456 nm), red (Sr,Ca)AlSiN3:Eu2+ phosphors (with a spectral emission at around 623 nm), and transparent silicone gels. Experimental temperature results are compared with those of micro-thermocouple (μ-TC) and infrared thermal imaging (TI), and fairly good agreements can be noticed. However, the spatial resolution of this proposed method is more than one order of magnitude higher than that of TI method, and the proposed method provides more detailed surface temperature information of phosphors than the latter. Therefore, we believe that this proposed method can serve as useful tools for the non-contact measurement of PSTD in pc-LEDs with or without optics lens.