Design of a sensitive uncooled therms imager based on a liquid crysta Fabry-Perot interferometer

摘要

Microbolometers are the dominant technology for uncooled thermal imaging; however, devices based on a direct retardation measurement of a liquid crystal (LC) transducer pixel have been shown to have comparable sensitivity. In this paper, an approach for increasing LC transducer sensitivity utilizing an etalon structure is considered. A detailed design for an LC resonant cavity between dielectric mirrors is proposed and the performance is evaluated numerically. The measured quantity is the transmission of a visible wavelength through the etalon, which requires no thermal contact with the IR sensor. Numerical and analytical calculations that consider a 470 nm thick LC pixel demonstrate that the change in transmitted intensity with temperature is 26 times greater in the device based on a resonant structure than in a device based on a direct retardation measurement. Finally, the paper discusses how the dielectric mirror materials, dimensions of the resonant cavity structure, and expected process tolerances affect the sensitivity of the device. (C) 2018 Optical Society of America