Micro UV detector
Inventors
Sickenberger, David W. • Cabalo, Jerry B. • Sickenberger, Richard
Assignees
United States Department of the Army
Publication Number
US-7375348-B1
Publication Date
2008-05-20
Expiration Date
2025-11-03
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Abstract
A biological aerosol detector is provided. The biological aerosol detector uses a semiconductor optical source with an ultraviolet emission band to excite biological molecules in an aerosol sample. Filtering optics are configured to attenuate radiation from a secondary emission band of the optical source to prevent false signals due to scattering of secondary emission band radiation from non-biological molecules. An intake/exhaust manifold that includes an intake pipe that fits within a concentric exhaust pipe is also provided. The intake/exhaust manifold planarizes the flow of the sampled aerosol to maximize the time of irradiation. An electrostatic sampling grid is also provided to selectively draw biological molecules having a net charge into the optical chamber.
Core Innovation
The invention provides a biological aerosol detector that employs a semiconductor optical source with an ultraviolet emission band to excite biological molecules in an aerosol sample. This detector includes filtering optics designed to attenuate radiation from a secondary emission band of the optical source, thus preventing false signals caused by scattering of this secondary emission band radiation from non-biological molecules. The detector further incorporates an intake/exhaust manifold with an intake pipe concentric to an exhaust pipe that planarizes aerosol flow to maximize irradiation time. Additionally, an electrostatic sampling grid selectively draws charged biological molecules into the optical chamber.
The problem being addressed stems from the use of semiconductor ultraviolet optical sources (SUVOS) in biological aerosol detection wherein these sources emit both a primary ultraviolet emission band capable of eliciting fluorescence from biological molecules and a secondary longer wavelength emission band. The secondary emission overlaps and can interfere with fluorescence signals, as its radiation is scattered by particles in the optical cavity, potentially causing false positive signals that do not correspond to biological molecules. Thus, reducing the influence of the secondary emission band is necessary to improve accuracy.
To solve this problem, the detector includes filtering optics such as dichroic mirrors, optical filters, and lenses configured to reflect or transmit specific emission bands to attenuate the unwanted secondary emission band. The intake/exhaust manifold design allows sampled aerosols to be introduced and exhausted in the same plane, thereby increasing residence time in the optical cavity for improved excitation. The electrostatic sampling grid, powered to produce an electric field across electrical grids, enhances sampling by attracting charged biological aerosol molecules selectively. These combined features aim to enhance detection specificity and sensitivity of biological aerosols.
Claims Coverage
The patent includes three main independent claims covering different aspects of the biological aerosol detector: optical filtering for emission band attenuation, combined intake/exhaust manifold design, and electrostatic sampling with associated detection circuits.
Biological aerosol detector with optical filtering and control aperture
The detector includes an excitation source with primary and secondary emission bands where the primary band excites the sample. Filtering optics attenuate radiation in the secondary emission band. An elliptical mirror housing forms the optical cavity, and an orifice made of UV absorptive material acts as a control aperture to limit stray radiation entering the cavity.
Combined intake and exhaust gas manifold for aerosol sampling
The detector has a manifold passing through the housing that collects aerosol samples into the optical cavity and exhausts them. The intake and exhaust sampling occur in the same plane. The manifold includes an intake pipe surrounded by a shorter exhaust pipe over part of its length, and an end cap with a face plate allowing the intake pipe to pass through.
Electrostatic sampling system with electrical grids and detection correlation
The detector comprises a housing with two holes along a sampling axis, electrical grids on either side generating an electric field to preferentially sample molecules with net charge. The grids may be plates or meshes. The system can include a Faraday ion detector and an optical detection circuit, with a correlation circuit (such as temporal coincidence) correlating optical fluorescence and ion signals for enhanced detection.
These inventive features together provide enhancements in selective excitation, aerosol sampling, signal filtering, and detection correlation to improve the specificity and sensitivity of biological aerosol detection.
Stated Advantages
Attenuates radiation from the secondary emission band to reduce false positive fluorescence signals from non-biological particles.
Increases the time aerosol samples are irradiated by planarizing intake and exhaust flows, improving excitation likelihood.
Selective electrostatic sampling enhances detection of biological aerosols that possess net electrical charges.
Combination of optical and ion detection with signal correlation enhances discrimination of biological aerosol signals from background.
Documented Applications
Detection of potentially harmful biological aerosols present after a biological agent attack or industrial accident.
Detection and discrimination of different biological molecules such as proteins, flavinoids, and metabolite products in aerosol samples.
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