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Optical path switching based differential absorption radiometry for substance detection

  • US 6,057,923 A
  • Filed: 04/13/1999
  • Issued: 05/02/2000
  • Est. Priority Date: 04/20/1998
  • Status: Expired due to Fees
First Claim
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1. A system for detecting a substance comprising:

  • an optical path switch for receiving radiation passing along a sample path of interest, said optical path switch dividing said radiation into a time series of alternating first polarized components and second polarized components orthogonal to said first polarized components, said optical path switch transmitting said first polarized components along a first optical path and said second polarized components along a second optical path;

    a first gasless optical filter train disposed in said first optical path for filtering said first polarized components to isolate at least a first wavelength band wherein first filtered radiation is generated;

    a second gasless optical filter train disposed in said second optical path for filtering said second polarized components to isolate at least a second wavelength band wherein second filtered radiation is generated, wherein said first wavelength band and said second wavelength band are unique and wherein spectral absorption of a substance of interest is different at said first wavelength band as compared to said second wavelength band;

    a beam combiner disposed to receive said first filtered radiation and said second filtered radiation for combining said first filtered radiation and said second filtered radiation to form a combined beam of radiation; and

    detector means disposed to monitor magnitude of at least a portion of said combined beam alternately at said first wavelength band and said second wavelength band as an indication of the concentration of said substance in said sample path.

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