Optical Design of Micro-Ledarrays for Photoplethysmography Sensor

With the widespread adoption of wearable smart health monitoring devices, the performance of their core component that the PPG sensor has become increasingly critical. Traditional PPG sensors face limitations such as bulky size, high power consumption, and slow response in their LED light sources, significantly constraining device battery life and measurement accuracy. To address these limitations, this study proposes replacing traditional LED chips with Micro-Led chips based on third-generation semiconductor technology as the light source for PPG sensors. Single-Channel PPG sensor models were constructed using both traditional LED chips and Micro-Led arrays.Based on the Beer-Lambert law and the Henyey-Greenstein function, a multi-layer skin tissue model was developed in TracePro. Monte Carlo-Based ray tracing simulations were employed to evaluate key performance metrics, including radiant flux on the detector and illumination uniformity. Comparative analysis revealed that the PPG sensor utilizing Micro-Led arrays outperformed its traditional LED counterpart under identical drive currents. Specifically, it demonstrated higher irradiance and superior illumination uniformity, with detector light intensity distribution uniformity improving by 5~6%. These findings validate the performance advantages of Micro-Led technology in enhancing PPG sensors, providing valuable insights for developing next-generation miniaturized, low-power blood oxygen monitoring sensing devices.