Browse Prior Art Database

In-Situ or Remote Sizing of Airborne Particles

IP.com Disclosure Number: IPCOM000034045D
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-26
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Hiller, B: AUTHOR

Abstract

An elastic light-scattering technique for the sizing of airborne particles is described. The ambiguity problem in particle sizing which arises from the spatial nonuniformity of light beams is solved by means of two concentric beams of different diameter and color. A clear distinction between large particles near the edge of the beam and small particles near the beam center can be made. The two beams differ in diameter by a factor of 1.5 to 2. Rather than using one of the beams as a trigger as with previous techniques, the ratio of the peak intensities of the scattering signal from both beams is used to compute the distance between particle trajectory and beam center. The corresponding center intensity can then be calculated and can be used to size particles via scattering computations or calibration.

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In-Situ or Remote Sizing of Airborne Particles

An elastic light-scattering technique for the sizing of airborne particles is described. The ambiguity problem in particle sizing which arises from the spatial nonuniformity of light beams is solved by means of two concentric beams of different diameter and color. A clear distinction between large particles near the edge of the beam and small particles near the beam center can be made. The two beams differ in diameter by a factor of 1.5 to 2. Rather than using one of the beams as a trigger as with previous techniques, the ratio of the peak intensities of the scattering signal from both beams is used to compute the distance between particle trajectory and beam center. The corresponding center intensity can then be calculated and can be used to size particles via scattering computations or calibration. This technique can be implemented either in a remotely located sampling particle counter or as an in-situ apparatus. Support a particle passes through two beams of different wavelengths which are concentric and have the center intensities I0,1 and I0,2 . The respective beam radii (measured at the 1/e2 points) are w1 and w2 . They can be either calculated, if diffraction-limited optics are used, or measured with various techniques as can be the ratio of the beam center intensities I0,1/I0,2 . The shortest distance between particle trajectory and beam center is r. Two detectors (each sensitive to the color of a different beam) will pr...