Title:
METHOD AND APPARATUS FOR OPERATING A LASER IN AN EXTINCTION-TYPE OPTICAL PARTICLE DETECTOR
Document Type and Number:
WIPO Patent Application WO2005079230
Kind Code:
A3
Abstract:
An optical particle detection systems (100) comprises laser source (105) that produces laser beam (130) in response to drive current (I) having amplitude that reaches lasing threshold. Beam (130) is characterized by mode-hopping noise energy produced by spurious switching of laser operating modes. Beam (130) propagates through view volume (115), through which stream of target particles immersed in carrier fluid (155) flows, to light-extinction type detector (120), which produces detection signal (145). Signal generator (125) produces drive current (I) such that its amplitude transitions across lasing threshold by selected amount and at selecteed frequency to purposefully cause beam (130) to operate simultaneously in multiple lasing modes. The selected amount and frequency cooperate to spread mode-hopping noise energy over a spectral range established by the number of simultaneously operating lasing modes, such that detector (120) does not appreciably respond to mode-hopping noise energy when producing signal (145).
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Inventors:
GIRVIN KENNETH L (US)
REED ADAM J (US)
REED ADAM J (US)
Application Number:
PCT/US2005/003564
Publication Date:
August 31, 2006
Filing Date:
February 04, 2005
Export Citation:
Assignee:
HACH ULTRA ANALYTICS INC (US)
GIRVIN KENNETH L (US)
REED ADAM J (US)
GIRVIN KENNETH L (US)
REED ADAM J (US)
International Classes:
G01N15/02; G01N15/14; G01N21/00
Foreign References:
| US6784981B1 | 2004-08-31 | |||
| US5701176A | 1997-12-23 |
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