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Improved particle sensor and method for assaying a particle

  • US 5,467,189 A
  • Filed: 01/12/1995
  • Issued: 11/14/1995
  • Est. Priority Date: 01/22/1993
  • Status: Expired due to Term
First Claim
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1. In a particle sensor containing gas molecules and including (a) a first elliptical mirror with a cavity, a first major axis and primary and secondary focal points along such first major axis, (b) a particle-illuminating beam of light having a wavelength and extending along a beam axis intersecting the primary focal point, and (c) an inlet for introducing airborne particles into a sensor view volume, the improvement wherein:

  • a light detector is at the secondary focal point;

    the region between the primary focal point and the light detector is substantially unobstructured;

    the primary focal point of the first mirror is coincident with the view volume;

    the sensor includes a second mirror having a second major axis offset along the beam axis and spaced from the first major axis, the second mirror reflecting light scattered substantially only by gas molecules; and

    the beam axis and the first major axis define an angle greater than 0°

    therebetween;

    whereby particles having a maximum dimension substantially less than the wavelength are detected.

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