Laser spectroscopy system
Inventors
Dottery, Ed • Waterbury, Rob • Stefano, Chris • Walters, Roy • Rose, Jeremy • Vilardi, Frank
Assignees
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Publication Number
US-8125627-B2
Publication Date
2012-02-28
Expiration Date
Abstract
A spectroscopy system including first and second lasers. The first laser is triggered to induce a plasma, such as on a surface of a target at a stand-off distance from the target. The second laser stimulates amplified emissions from the plasma detected by one or more spectroscopes. The gain induced by the second laser detects traces of explosives and other substances on surfaces at stand-off distances. The spectroscopy systems use the same telescopic optics to collect emissions from the detection surface and activated at or just before the peak emission intensity useful for detecting element signatures and intensity ratios from the trace elements in the plasma.
Core Innovation
The invention relates to laser spectroscopy using Townsend Effect Plasma Spectroscopy (TEPS) in a stand-off configuration. A first pulsed solid-state laser induces a spark plasma on a target at stand-off distance, and a spectroscope detects emissions from the induced plasma. The background problem is the need to perform stand-off detection of trace substances at useful distances while improving signal gain for spectroscopic identification.
A second laser is temporally and optically aligned with the first laser to stimulate amplified plasma emissions. The second laser operates at eye-safe wavelengths, including an example of a CO2 laser at approximately 10.6 μm, and the timing between the first and second lasers is controlled with a microsecond-scale inter-laser delay. Optical collection elements are activated near peak emission timing to support stand-off detection.
The invention further describes use of TEPS with Raman spectroscopy using shared optics to form a dual TEPS/RAMAN configuration. The amplified emission spectra and Raman data are used for identification based on comparison to signatures, including lookup-table (LUT) signatures and chemometrics for determining the identity of materials. Documented results report substantial gain improvements and amplified spectral features intended to improve detection of trace explosives and chemicals.
Claims Coverage
The claims coverage describes stand-off TEPS with a second laser for amplified plasma emissions and identifies 2 inventive features.
Temporally and optically aligned second laser
A second laser is aligned with a first pulsed solid-state laser to stimulate amplified plasma emissions, with microsecond-scale inter-laser delay control.
Dual TEPS/RAMAN configuration
TEPS is combined with Raman spectroscopy using shared optics for identification based on signatures and chemometrics.
The inventive features center on amplified stand-off plasma emissions using a second laser and on a shared-optics TEPS/RAMAN configuration for material identification.
Stated Advantages
Substantial gain improvements for amplified plasma emissions, reported approximately 25× to 300×.
Improved or novel spectral peaks and intensity ratios for trace explosives and chemicals for spectroscopic identification.
Eye-safe wavelength operation for stand-off laser-induced plasma spectroscopy.
Stand-off detection at useful distances, including approximately up to 20 m for laser-induced plasma spectroscopy and approximately 50–70 m using CO2 amplification.
Combined TEPS and Raman spectroscopy using shared optics for multispectral identification based on signatures and chemometrics.
Documented Applications
Stand-off detection and identification of trace explosives and trace chemicals using amplified plasma emissions and, in a dual configuration, Raman spectroscopy.
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