Particles counting apparatus and method having improved particle

Details Particles counting apparatus and method having improved particle Particles counting apparatus and method having improved particle

1998-07-10

2000-01-18

Font, Frank G.

Optics: measuring and testing

By particle light scattering

356335, 356336, 356338, G01N 1502, G01N 2100

Patent

active

060161949

ABSTRACT:
A particle counter (10) passes a sample stream of particles (72) through an elongated, flattened nozzle (16) and into a view volume (18) formed by an intersection of the sample stream and a laser beam (13). Scattered light (24) from the view volume is focused onto a linear array (32) of photodiode detectors (40) positioned such that a longitudinal length (70) of the view volume is imaged on the detectors. Because the sample stream produces nonuniform particle velocities along the longitudinal dimension of the view volume, for same-sized particles higher velocity particles will generate lower output amplitude signals than lower velocity particles. Therefore, the gain associated with each photo-detector element is adjustable to compensate for the nozzle velocity differences, laser beam intensity differences caused by beam divergence and fluctuations, optical path efficiency variations, and photo-detector element-to-element sensitivity differences.

REFERENCES:
patent: 4746215 (1988-05-01), Gross
patent: 4896048 (1990-01-01), Borden
patent: 5085325 (1992-02-01), Jones et al.
patent: 5642193 (1997-06-01), Girvin et al.
patent: 5726753 (1998-03-01), Sandberg
"Light Scattering Automatic Particle Counter", Japanese Industrial Standard, JIS B 9921, 1989, UDC 543.275.082.5:535.43:628.511.1, pp. 1-18.

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