Detection of organic vapors with active and passive sensors: a comparison

Abstract

Many organic compounds of medium complexity have their most characteristic spectral features in the 8–12-μm region of the IR. Both active and passive sensors can be used for detection of these compounds. The active systems are based on pulsed CO2 lasers and direct detection sensors operated in either the distributed (range resolved) or topographic reflector modes. Passive sensors are based on natural temperature differences which exist between the background and target cloud. The effects of throughput, collecting aperture size, electronic bandwidth, background noise, speckle noise, laser energy, and temperature difference are discussed for active and passive spectral sensors. The noise equivalent concentration path length product is used to define performance for both passive and active sensors. The computed results are compared to recently published reports.