Optical path switching based differential absorption radiometry for substance detection
First Claim
1. A system for detecting a substance, comprising:
- means for receiving radiation passing along a sample path of interest;
means for dividing said radiation into a time series of alternating first polarized components and second polarized components orthogonal to said first polarized components;
means for routing said first polarized components along a first optical path and said second polarized components along a second optical path;
gasless means for passing all wavelengths of said first polarized components except at least a first wavelength band wherein first filtered radiation excluding said at least first wavelength band is generated;
means 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;
means for combining said first filtered radiation and said second filtered radiation to form a combined beam of radiation; and
means for monitoring magnitude 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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Abstract
An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.
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Citations
22 Claims
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1. A system for detecting a substance, comprising:
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means for receiving radiation passing along a sample path of interest;
means for dividing said radiation into a time series of alternating first polarized components and second polarized components orthogonal to said first polarized components;
means for routing said first polarized components along a first optical path and said second polarized components along a second optical path;
gasless means for passing all wavelengths of said first polarized components except at least a first wavelength band wherein first filtered radiation excluding said at least first wavelength band is generated;
means 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;
means for combining said first filtered radiation and said second filtered radiation to form a combined beam of radiation; and
means for monitoring magnitude 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. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for detecting a substance, comprising:
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means for receiving radiation passing along a sample path of interest;
means for dividing said radiation into a time series of alternating first polarized components and second polarized components orthogonal to said first polarized components;
means for routing said first polarized components along a first optical path and said second polarized components along a second optical path;
means for reflecting all wavelengths of said first polarized components except at least a first wavelength band wherein first filtered radiation excluding said at least first wavelength band is generated;
means for passing all wavelengths of said second polarized components except at least a second wavelength band wherein second filtered radiation excluding said second wavelength band 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;
means for combining said first filtered radiation and said second filtered radiation to form a combined beam of radiation;
means, disposed to receive said combined beam, for filtering the combined beam, said means for filtering having a bandpass characteristic that spans said excluded first and second wavelength bands; and
means for monitoring magnitude of said combined beam received from the filter alternately at said first wavelength band and said second wavelength band as an indication of the concentration of said substance in said sample path. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A system for detecting a substance comprising:
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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 routing 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 reflecting all wavelengths of said first polarized components except at least a first wavelength band wherein first filtered radiation excluding said at least first wavelength band is generated;
a second gasless optical filter train disposed in said second optical path for reflecting all wavelengths of said second polarized components except at least a second wavelength band wherein second filtered radiation excluding said at least second wavelength band 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;
a filter disposed to receive said combined beam of radiation and having a bandpass characteristic that spans said excluded first and second wavelength bands; and
detector means disposed to monitor magnitude of at least a portion of said combined beam received from said filter alternately at said first wavelength band and said second wavelength band as an indication of the concentration of said substance in said sample path. - View Dependent Claims (16, 17, 18, 19)
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20. A substance detection system comprising:
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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 routing 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 reflecting all wavelengths of said first polarized components except those in a first wavelength band wherein first filtered radiation excluding said first wavelength band is generated;
at least one gas correlation cell disposed in said first optical path for filtering one of said first polarized components and said first filtered radiation at spectral regions different from that of said first wavelength band;
a second gasless optical filter train disposed in said second optical path for reflecting all wavelengths of said second polarized components except those in a second wavelength band wherein second filtered radiation excluding said second wavelength band 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 vacuum cell disposed in said second optical path;
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;
a filter disposed to receive said combined beam of radiation and having a bandpass characteristic that spans said excluded first and second wavelength bands;
first detecting means disposed to monitor magnitude of at least a portion of said combined beam received from the filter alternately at said first wavelength band and said second wavelength band as an indication of the concentration of said substance in said sample path; and
second detecting means disposed to sense a difference in intensity between said first filtered radiation and said second filtered radiation at said spectral regions to measure the concentration of at least one gas species in said sample path. - View Dependent Claims (21, 22)
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Specification