Physical Sciences Inc. has developed a standoff deep ultraviolet (DUV) Raman sensor for the detection of explosive residues. The sensor is based on a solid-state DUV excitation source coupled with a Spatial Heterodyne Spectrometer receiver. The sensor measures Raman signals across a ~830–2680 cm-1 spectral range from a 2.6 cm2 interrogation area from a 1 m standoff in a single snapshot with a 17 cm-1 spectral resolution. Acquired spectra are processed through an on-board deep learning spectral correlation algorithm that provides real-time target identification. Developmental testing of the sensor has been conducted in a laboratory environment against explosive simulants including potassium chlorate, ammonium nitrate, and urea in bulk form as well as residues deposited on various substrates including plastic, glass, and metals. These measurements have demonstrated the system’s ability to measure Raman spectra and identify targets in 1 to 120 seconds.
Physical Sciences Inc. has developed an ultra-compact shortwave infrared (SWIR) staring mode hyperspectral imaging (HSI) sensor with an additional visible full motion video (FMV) capability. The innovative HSI design implements a programmable micro-electromechanical system entrance slit that breaks the interdependence between vehicle speed, frame rate, and spatial resolution of conventional push-broom systems and enables staring-mode operation without cooperative motion of the host vehicle or aircraft. The FMV and HSI components fit within 1000 cm3, weigh a total of 2.1 lbs., and draw 15 W of power. The sensor mechanical design is compatible with gimbal-based deployment allowing for easy integration into ground vehicles or aircrafts. The FMV is capable of achieving NIRS-6 imagery over a 6°×6° field-of-view (FOV) at a 1500 ft. standoff. The SWIR HSI covers a spectral range of 900-1605 nm with a 15 nm spectral resolution, and interrogates a 5°×5° FOV per 1.6 s with a 2.18 mrad instantaneous FOV (1 m ground sample distance at 1500 ft.). A series of outdoor tests at standoffs up to 300 ft. have been conducted that demonstrate the payload’s capability to acquire HSI information. The payload has direct utility towards diverse remote sensing applications such as vegetation monitoring, geological mapping, surveillance, etc. The data product utility is demonstrated through the spectral identification of materials (e.g. foam and cloth) placed in the sensor’s FOV.
There is an on-going need for sensor technologies capable of providing non-contact chemical detection and identification in the defense community. Here, we present the development of a standoff deep ultraviolet (DUV) Raman sensor for the detection of explosive residues. The sensor is based on a solid-state DUV excitation source coupled with a Spatial Heterodyne Spectrometer (SHS) receiver. The sensor is designed to detect Raman signals from a 4 cm2 area surface at a 1 m standoff. Detection and identification is achieved by correlating measured Raman signatures with high fidelity library spectra. The DUV excitation enables operation in a solar blind spectral region, leverages v4 cross section scaling and resonance enhancement of Raman signatures, and minimizes the impact of sample fluorescence. The SHS receiver provides a ~100× higher etendue than conventional slit-based spectrometers in a compact and rugged form factor, allowing for high performance field use. This work describes the system design and architecture of the Raman sensor prototype. Developmental standoff Raman measurements with the sensor using bulk liquid and solid samples are presented. Traceability to detection at the µg/cm2 scale is demonstrated and future improvements to increase system standoff are discussed.
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