Standoff trace chemical detection with active infrared spectroscopy

A process for scanning a target located at a distance of at least 3 meters from a stand-off detector to detect one or more materials thereon, the process comprising:

• scanning the target with a source pulse beam emitting in a spectral range of approximately 2 to 12 μm generated by a supercontinuum (SC) laser source, wherein prior to reaching the target, the source pulse beam is spectrally modulated by a refraction-based interferometric modulator and sampled by an optical component to obtain a source reference measurement signal;
• receiving at an optical receiver a reflected source pulse beam from the target and the source reference measurement signal from the optical component;
• detecting by at least one infrared detector the target reflected source pulse beam from the target and the source reference measurement signal source reference measurement signal as a series of interferograms;
• digitizing the interferograms by a digitizer;
• processing the interferograms to produce spectrograms to detect the inclusion of one or more materials on the target;
• and
• detecting an internal continuous wave reference beam generated by an internal diode laser, wherein the internal continuous wave reference beam is used for collection of fringe timing data from the series of interferograms and used by the processor for producing the spectrograms and further wherein processing the interferograms includes calculating a full Fourier transform matrix, wherein each term is given by the formula:
• F(ν,α)=e−i2πν×OPD(α,n(ν))
• further wherein, ν is the wavenumber in cm−1 and α is a refractor angle associated with each interferogram, and n(ν) is the wavenumber-dependent index of refraction of the refractor.