Fundamental problems of incoherent optical heterodyne detection are analyzed. Output of the heterodyne detection depends on the spatial and temporal coherences of incoming incoherent signal light on the photodetector surface. The directivity of optical heterodyne detection is concluded to be the same as with that of direct detection in an ideal case in which the image of the object is well focused on the photodetector surface. This incoherent heterodyne detection is applied to air pollution monitoring. In the laboratory, the absorption spectra due to NH(3), Freon, and SF(6) are measured using an incoherent light source, and the concentrations of each gas were determined by using the least-squares method.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.