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Proceedings Paper

Waveguide infrared spectrometer platform for point and standoff chemical sensing
Author(s): Suneet Chadha; Pat Henning; Frank Landers; Ani Weling
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Paper Abstract

Advanced autonomous detection of chemical warfare agents and toxic industrial chemicals has long been a major military concern. At present, our capability to rapidly assess the immediate environment is severely limited and our domestic infrastructure is burdened by the meticulous procedures required to rule out false threats. While significant advances have recently been accomplished in remote spectral sensing using rugged FTIRs and point detectors, efforts towards low cost chemical discrimination have been lacking. Foster-Miller has developed a unique waveguide spectrometer which is a paradigm shift from the conventional FTIR approach. The spectrometer provides spectral discrimination over the 3-14 μm range and will be the spectrometer platform for both active and passive detection. Foster-Miller has leveraged its innovations in infrared fiber-optic probes and the recent development of a waveguide spectrometer to build a novel infrared sensor platform for both point and stand-off chemical sensing. A monolithic wedge-grating optic provides the spectral dispersion with low cost thermopile point or array detectors picking off the diffracted wavelengths from the optic. The integrated optic provides spectral discrimination between 3-12 μm with resolution at 16 cm-1 or better and overall optical throughput approaching 35%. The device has a fixed cylindrical grating bonded to the edge of a ZnSe conditioning “wedge”. The conditioning optic overcomes limitations of concave gratings as it accepts high angle (large FOV) light at the narrow end of the wedge and progressively conditions it to be near normal to the grating. On return, the diffracted wavelengths are concentrated on the discrete or array detector (pixel) elements by the wedge, providing throughput comparable to that of an FTIR. The waveguide spectrometer coupled to ATR probes, flow through liquid cells or multipass gas cells provides significant cost advantage over conventional sampling methodologies. We will present the enabling innovations along with present performance, sensitivity expectations and discrimination algorithm strategy.

Paper Details

Date Published: 8 March 2004
PDF: 13 pages
Proc. SPIE 5269, Chemical and Biological Point Sensors for Homeland Defense, (8 March 2004); doi: 10.1117/12.519426
Show Author Affiliations
Suneet Chadha, Foster-Miller, Inc. (United States)
Pat Henning, Foster-Miller, Inc. (United States)
Frank Landers, Foster-Miller, Inc. (United States)
Ani Weling, Foster-Miller, Inc. (United States)

Published in SPIE Proceedings Vol. 5269:
Chemical and Biological Point Sensors for Homeland Defense
Arthur J. Sedlacek III; Richard Colton; Tuan Vo-Dinh, Editor(s)

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