Remote Compact Robotic-Optical Sensor for Long Range Chemical Detection
Technical Report,01 Jul 2015,30 Sep 2018
Univ of Hawaii Honolulu United States
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In the field of remote chemical detection using active laser interrogation, it is generally accepted that for a longer detection range, the size of the system must be larger in order to compensate for the signal loss due to the lower cross-section of collection optics. Using 8 diameter telescope and 100 mJpulse laser power, we have successfully detected various chemicals from a distance of 430 m using Raman spectroscopy. To the best of our knowledge, Dr. Lasernas group in Spain Univ. of Malaga holds the world record for conducting LIBS at the distance of 130 m using a large system utilizing a pulsed laser with 750 mJpulse at 1064 nm. Under this research project, we developed a novel two component approach that helps to obtain remote Raman and LIBS spectra of targets at distance of 246 m with 3 mJpulse in daytime and fast detection time of 1 s using a small remote RamanLIBS system with 3 diameter collection optics. The two components of the method are i a small spectroscopy system utilizing 76 mm diameter collection optics and ii a small remote lens near the target. Remote Raman spectra of various chemicals could be obtained with integration time of 1 s. Remote LIBS spectra of minerals from a distance of 246 m were obtained using single laser pulse of 3 mJpulse energy. This is a new world record for performing remote LIBS and also using low laser pulse energy. This method is also applicable for developing future eye safe remote LIBS system using low power lasers in the IR region, e.g. 1550 nm laser. This research work demonstrates a simple approach that significantly improves remote Raman and LIBS capabilities for long range chemical detection with compact low laser power Raman and LIBS systems.
- Miscellaneous Detection and Detectors