Rectangular Parallelepiped-shaped Optical Cell for Sensing Particular Matter with Ultra-low Concentration by Mid-infrared Absorption

초록

As the effects of air pollution and climate change on public health are increasingly concerned, air-quality monitoring has been received much attractions [1]. In particular, as mobile devices such as smart phone and smart watch become popular, demand on wearable sensing devices to monitor air quality is gradually increasing. Recently, a compact optical cell was introduced to sense a dilute gas (particulate matter) with laser absorption spectroscopy, where the cell with a shape of a closed disk was used to increase the optical path length through a gas sample by multiple passing of a laser beam [2]. In our research, a sensing device using a conventional light source instead of a laser has been studied to reduce the device cost. If a blackbody radiator with a narrow band-pass ?lter is used as a mid-infrared source, however, the optical path length increased by the multiple re°ection within an optical cell becomes diverse according to the direction of each ray emanated from the radiator due to the beam divergence. Consequently, this ambiguity of the increased optical path length may impair the sensitivity of the device.