Pixelless Upconversion Imaging Based on Surface Microsphere Coupled Light Emitting Diodes

High performance infrared imaging devices are widely used in environmental monitoring, surveillance, and national defense. Pixelless upconversion imaging devices hold great promise for the future of large-format infrared imaging. In this work, we propose a microsphere (MS) structure coupled pixelless upconversion imaging device and demonstrate the upconversion imaging of the blackbody hot spot. In contrast to previous studies, light extraction efficiency (LEE) of the device is significantly improved. An upconversion efficiency comparable to that of the traditional grating structure was achieved. A systematic investigation is carried out theoretically, and it is found that the external quantum efficiency of the light emitting diodes is the main contribution to the upconversion efficiency, rather than the coupling efficiency of the quantum well detector. An optimized micro-structure coupled pixelless imaging device with high upconversion efficiency is also presented. This work provides ideas and experience for subsequent large-format, high-efficiency, and high-speed pixelless upconversion infrared imaging.