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Proceedings Paper

Active infrared hyperspectral imaging system using a broadly tunable optical parametric oscillator
Author(s): G. P. A. Malcolm; G. T. Maker; G. Robertson; M. H. Dunn; D. J. M. Stothard
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Paper Abstract

The in situ identification and spatial location of gases, discrete liquid droplets and residues on surfaces is a technically challenging problem. Active Infrared (IR) hyperspectral imaging is a powerful technique that combines real-time imaging and optical spectroscopy for "standoff" detection of suspected chemical substances, including chemical warfare agents, toxic industrial chemicals, explosives and narcotics. An active IR hyperspectral imaging system requires a coherent, broadly tunable IR light source of high spectral purity, in order to detect a broad range of target substances. In this paper we outline a compact and power-efficient IR illumination source with high stability, efficiency, tuning range and spectral purity based upon an optical parametric oscillator (OPO). The fusion of established OPO technology with novel diode-pumped laser technology and electro-mechanical scanning has enabled a broadly applicable imaging system. This system is capable of hyperspectral imaging at both Near-IR (1.3 - 1.9 μm) and Mid-IR (2.3 - 4.6 μm) wavelengths simultaneously with a line width of < 3 cm-1. System size and complexity are minimised by using a dual InGaAs/InSb single element detector, and images are acquired by raster scanning the coaxial signal and idler beams simultaneously, at ranges up to 20 m. Reflection, absorption and scatter of incident radiation by chemical targets and their surroundings provide a method for spatial location, and characteristic spectra obtained from each sample can be used to identify targets uniquely. To date, we have recognized liquids in sample sizes as small 20 μl-and gases with sensitivity as high as 10ppm.m-at detection standoff distances > 10 m.

Paper Details

Date Published: 9 October 2009
PDF: 9 pages
Proc. SPIE 7486, Optics and Photonics for Counterterrorism and Crime Fighting V, 74860H (9 October 2009); doi: 10.1117/12.833602
Show Author Affiliations
G. P. A. Malcolm, M Squared Lasers Ltd. (United Kingdom)
G. T. Maker, M Squared Lasers Ltd. (United Kingdom)
G. Robertson, M Squared Lasers Ltd. (United Kingdom)
M. H. Dunn, Univ. of St. Andrews (United Kingdom)
D. J. M. Stothard, Univ. of St. Andrews (United Kingdom)

Published in SPIE Proceedings Vol. 7486:
Optics and Photonics for Counterterrorism and Crime Fighting V
Colin Lewis, Editor(s)

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