18 Mar 2003
An infrared spectroscopy setup that can detect biological spores 3 km away is described in the current Optics Express.
A field trial in the US suggests that Fourier-Transform infrared (FTIR) spectroscopy can detect clouds of biological aerosols at a distance of 3 km. The findings were reported in the current issue of Optics Express by Avishai Ben-David of the Science and Technology Corporation, US. (Optics Express 11 418)
Ben-David reports that a passive FTIR spectrometer was able to detect and recognize spores of Bacillus subtilis niger (BG), a bacterial spore similar to Anthrax. The measurements took place in Ohio last summer and in the presence of dust.
In the tests, road dust was generated by two vehicles driven along a dirt track and then just 3 minutes later a 5 s puff of 800 g of BG was released into the open air. The temperature difference (thermal contrast) between the dust and the BG aerosol was just 1 K (1 °C). A state-of-the-art FTIR Michelson spectrometer then made a series of measurements between 800 and 1200 cm-1 at a distance of 3 km.
According to Ben-David, the key to the detection success was the use of a hyperspectral detection, identification and estimation algorithm combined with advanced signal processing techniques to subtract the undesirable background spectra. He now plans to run further tests.
"The results are encouraging and suggest for the first time the feasibility for remotely detecting biological aerosols with passive FTIR sensors," says Ben-David in his paper. "It is an important first step and more controlled experiments are planned where the effect of different meteorological conditions and distances will be studied."
Oliver Graydon is editor of Optics.org and Opto & Laser Europe magazine.