抄録
The performance of an atmospheric gas monitoring system that is local, real-time, non-contacting and portable was examined. An experimental system was built using Pb Sn Te lead-salt infrared diode laser and Hg Cd Te infrared detectors operating in 7.6μm band. Atmospheric absorption spectra over 1 cm-1 instead of absorption at, a singleline, was involved to obtain the gas density. Experiments were performed for methaneand the sensitivity was found to be 0.3 ppm for one meter optical-path and for 4 secondsof single spectral scanning period. This value was mostly limited by etalon fringes (optical-path noise). Methods to suppress the fringe are proposed. Its statisticalfeatureswere investigated and the shortest measurement time without sacrificing theaccuracy is anticipated to be as short as that of responses of the current devices 4.7ms.
