Chemical vapor detection with a multispectral thermal imager

Detection of chemical vapor clouds has been a military concern since the first use of chemical warfare. Growing concern for environmental pollution has additionally driven development of remote chemical vapor detectors.1 The FUR (forward looking infrared) is an 8to 12-rim thermal imager widely used in the military for target acquisition and night vision. Chemical vapors are spectrally active in the 8to 12-iim region. There have been several military programs to adapt the FLIR for chemical detection.25 A navy FLIR has been deployed for chemical sensing.4 It is a standard common module FLIR modified with bandpass spectral filters. Agent detection is made by the operator based on the viewed scene. Army requirements specify an autonomous detection system not dependent on an operator for an alarm decision. To meet Abstract. Detection of chemical vapors with a remote sensor is necessary for both military defense and civilian pollution control. The thermal imager is a natural instrument from which to build a chemical sensor since most chemical vapors of interest are spectrally active in its operating wavelength range. A system has been designed to place a chemical detection capability as an adjunct function in a military thermal imager. An additional detector array, which is spectrally filtered at the focal plane, is added to the imager. Real-time autonomous detection and alarm is also required. A detection system model by Warren, based on a Gaussian vapor concentration distribution is the basis for detection algorithms. Algorithms recursive in both time and spectral frequency have been derived using Kalman filter theory. Adaptive filtering is used for preprocessing clutter rejection. Various components of the detection system have been tested individually and an integrated system is now being fabricated.