Hazardous material analysis using mid-wave infrared hyperspectral imaging techniques

Abstract

The detection and identification of hazardous material is required in a wide range of application environments including military and civilian. Infrared (IR) absorption spectroscopy is a technique that can be used for material identification through comparing absorption spectra with reference data from a spectral library. The absorption spectrum of a compound is the result of light at certain wavelengths being absorbed through molecular vibrations of the compound. To build on this phenomenon, hyperspectral imaging can be used to add spatial information of the absorber. In this case, the IR source output, an optical parametric oscillator (OPO) operating at 1.5 to 1.7 μm in the short wave IR (SWIR) and 2.7 to 3.6 μm in the mid wave IR (MWIR), is raster scanned using a galvanometric mirror pair across a scene of interest. The resulting backscattered light is de-scanned through the same mirror pair and focussed onto point detectors and images in the IR are generated. This hyperspectral imaging instrument is a prototype that is currently being developed for a wide range of applications. If an absorber is present and the OPO wavelength is tuned to an absorption feature of this absorber, this interaction will appear as a dark area in the generated image. With the broad tunability of the OPO, a detailed absorption spectrum of the target compound can be recorded and used to aid material identification. This work presents a selection of results where explosive simulants and materials were investigated and analysed using the prototype instrument.