Standoff detection: classification of biological aerosols using laser induced fluorescence (LIF) technique

Abstract

The challenges of detecting hazardous biological materials are manifold: Such material has to be discriminated from other substances in various natural surroundings. The detection sensitivity should be extremely high. As living material may reproduce itself, already one single bacterium may represent a high risk. Of course, identification should be quite fast with a low false alarm rate. Up to now, there is no single technique to solve this problem. Point sensors may collect material and identify it, but the problems of fast identification and especially of appropriate positioning of local collectors are sophisticated. On the other hand, laser based standoff detection may instantaneously provide the information of some accidental spillage of material by detecting the generated thin cloud. LIF technique may classify but hardly identify the substance. A solution can be the use of LIF technique in a first step to collect primary data and -if necessary-followed by utilizing these data for an optimized positioning of point sensors. We perform studies on an open air laser test range at distances between 20 and 135 m applying LIF technique to detect and classify aerosols. In order to employ LIF capability, we use a laser source emitting two wavelengths alternatively, 280 and 355 nm, respectively. Moreover, the time dependence of fluorescence spectra is recorded by a gated intensified CCD camera. Signal processing is performed by dedicated software for spectral pattern recognition. The direct comparison of all results leads to a basic classification of the various compounds.

Development of bioaerosol lidar system

“…Experiments show that it can detect and distinguish bioaerosols [23] . In 2014, the 280nm and 355nm dual wavelength UV laser-induced fluorescence system proposed by German Aerospace Center for aerosol detection and classification realized the preliminary judgment of different kinds of compounds by using spectral pattern recognition software [24] . Through different data under multi-wavelength excitation, more specific fluorescence characteristics of bioaerosols can be obtained, and the classification accuracy of bioaerosols can be further improved.…”

An UltraViolet Laser-Induced Fluorescence (UV-LIF) system to detect, identify and measure the concentration of biological agents in the environment: a preliminary study

“…In literature, several studies show the capability of the LIF technique to detect and classify biological agents [7,8]. Currently, the main weakness of the LIF technique is connected to the…”

Standoff detection and classification of bacteria by multispectral laser-induced fluorescence

“…In cooperation with LDI Innovations (Estonia), we presented a setup for dual-excitation wavelength (280 nm, 355 nm) LIF detection and classification of different bioorganic substances [20,21]. The online classifier used therein relies on spectral feature extraction and selection and has been trained with a basic set of experimental spectra by bootstrap aggregation and a decision tree classification.…”