Patent ID: 6372184
Filing Date: 2002-04-16
Classification: G01N

Abstract:
A system for detecting the presence of liquid chemical agent droplets in air comprising:(a) paper that stains upon contact with said liquid chemical agent droplets; (b) an aperture exposure located above said paper and having means for being opened and closed and interposed between said paper and said air; (c) aperture exposure drive means operatively connected to said aperture exposure and serving as said means for being opened and closed and responsive to the presence and absence of a first control signal generated by an external control circuit for respectively opening and closing said aperture exposure; (d) a cassette for holding said paper; (e) cassette drive means responsive to the presence of second and third controls signals generated by said external control circuit for respectively moving said paper in first and second directions that are opposite from each other; (f) at least a first optical scanner providing a first optical beam and arranged so that said first optical beam intercepts said stain as said paper is being moved in said first direction in response to said second control signal, said first optical scanner having means for receiving said optical beam after it has passed through said paper and providing an electromagnetic spectrum representative of the chemical composition of said stain, said first optical scanner having means for converting said electromagnetic spectrum into a first digital signal serving as a first digital signature of a stain; (g) a light source applied to said first optical scanner serving as the excitation for said first optical beam; (h) a spectral filter wheel with rotatable means and having a predetermined number of selectable filters, said spectral filter wheel being interposed between said light source and said first optical scanners; (i) spectral filter wheel drive means connected to said rotatable means and responsive to a fourth control signal generated by said external control circuit so that said filters are selectively interposed between said light source and said first optical scanner; and (j) means for receiving and comparing said first digital signal against predetermined digital signals each representative of a particular liquid chemical agent and generating an alarm if there is a match between said first digital signal and any of said predetermined digital signals.