US Government As Represented by the Secretary of the Army

Dennis M Davis

Lynn D Hoffland

Mark G Rockley

William R Loerop

John T Ditillo

Robert T Kroutil

Michael S Desha

A short scan passive infrared remote sensor for detecting a target chemical pecies, located some distance from the center burst, includes a telescope for targeting a remote gas, a beam splitter means for splitting a beam from the target gas and sending one portion along a first path to an infrared detector and sending a second portion along a second path longer than the first path to the infrared detector. The second path is variable by providing a moving mirror a first distance away from the beam splitter which is 0.5 mm farther away from the beam splitter than the fixed mirror. By this arrangement, a mirror movement of only 0.5 mm is required to obtain an equivalent of 8 cm.sup.-1 spectral information for processing with time domain digital filters. The information from the infrared detector is converted from analog to digital and fed to a digital signal processor. The resulting interferogram is then filtered by a microprocessor using a FIR linear digital filter.

Short scan passive infrared remote sensor

A photoacoustic detector includes an evaporation space for receiving an onic vapor. The space is bounded by a window which is transparent to infrared radiation. A spectrometer irradiates the space with infrared radiation through the window to heat the vapor and acoustically modulate it at a frequency corresponding to the frequency of the infrared radiation. The acoustic modulations are picked up by a microphone which produces a signal which is amplified and used to form a characteristic spectrum. In this way gases or liquid in the space between the infrared source and the window can be detected by examining changes in the spectrum.

Gas phase photoacoustic detector for infrared spectroscopy

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Edgewood, MD, United States of America

Dennis M Davis