Method and apparatus for operating a laser in an...

Details Method and apparatus for operating a laser in an... Method and apparatus for operating a laser in an...

2006-02-21

2006-02-21

Toatley, Jr., Gregory J. (Department: 2877)

Optics: measuring and testing

For size of particles

C356S338000

Reexamination Certificate

active

07002682

ABSTRACT:
A light-extinction-type optical particle detection system comprises a laser producing a beam in response to a drive current amplitude reaching a lasing threshold, a view volume, and a light-extinction detector. The beam is characterized by mode-hopping noise energy produced by spurious switching of laser operating modes. The system comprises a signal generator producing the drive current such that its amplitude transitions across the threshold by a selected amount and at a selected frequency to cause the beam to operate simultaneously in multiple modes. The selected amount and frequency cooperate to spread the mode-hopping noise energy over a spectral range established by the number of modes, such that the detector does not appreciably respond to the mode-hopping noise energy.

REFERENCES:
patent: 5475235 (1995-12-01), Phillips et al.
patent: 6784981 (2004-08-01), Roche et al.
patent: 09-178645 (1997-07-01), None
Akira Arimoto, et al., “Optimum Conditions for the High Frequency Noise Reduction Method in Optical Videodisc Players,” published inApplied Optics, vol. 25, No. 9, May 1, 1986.
Masahiro Ojima, et al., “Diode Laser Noise at Video Frequencies in Optical Videodisc Players”, published inApplied Optics, vol. 25, No. 9, May 1, 1986.
K. Petermann, book entitledLaser Diode Modulation and Noise, Copyright 1988 by Kluwer Academic Publishers, Chapter 4, pp. 100 to 105.

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