We present initial results on the performance of a compressive sensing setup for Raman imaging spectroscopy for standoff trace explosives detection. Hyperspectral image reconstruction is demonstrated under low signal conditions and successful spatial separation of substances with close lying Raman peaks is shown.
Imaging Raman spectroscopy based on tunable filters is an established technique for detecting single explosives particles
at stand-off distances. However, large light losses are inherent in the design due to sequential imaging at different
wavelengths, leading to effective transmission often well below 1 %.
The use of digital micromirror devices (DMD) and compressive sensing (CS) in imaging Raman explosives trace
detection can improve light throughput and add significant flexibility compared to existing systems. DMDs are based on
mature microelectronics technology, and are compact, scalable, and can be customized for specific tasks, including new
functions not available with current technologies.
This paper has been focusing on investigating how a DMD can be used when applying CS-based imaging Raman
spectroscopy on stand-off explosives trace detection, and evaluating the performance in terms of light throughput, image
reconstruction ability and potential detection limits. This type of setup also gives the possibility to combine imaging
Raman with non-spatially resolved fluorescence suppression techniques, such as Kerr gating.
The system used consists of a 2nd harmonics Nd:YAG laser for sample excitation, collection optics, DMD, CMOScamera
and a spectrometer with ICCD camera for signal gating and detection.
Initial results for compressive sensing imaging Raman shows a stable reconstruction procedure even at low signals and
in presence of interfering background signal. It is also shown to give increased effective light transmission without
sacrificing molecular specificity or area coverage compared to filter based imaging Raman. At the same time it adds
flexibility so the setup can be customized for new functionality.
We present preliminary results on the performance of a basic stand-off Raman spectroscopy setup using coded apertures compared to a setup using a round-to-slit fiber for light collection. Measurements were performed using single 5 ns laser shots at 355 nm with a target distance of 5.4 meters on ammonium nitrate powder. The results show an increase in signal-to-noise ratio of 3-8 times when using coded aperture multiplexing compared to the fiber setup.