Infrared spectrometer
First Claim
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1. An infrared, IR spectrometer comprising:
- a first tunable IR laser for providing a first beam at a first wavelength;
a second tunable IR laser for providing a second beam at a second wavelength;
a first absorption cell arranged to receive both first and second beams;
a second absorption cell arranged to receive both first and second beams;
a first optical absorption detector arranged to detect said first wavelength;
a second optical absorption detector arranged to detect said second wavelength; and
an interlacer arranged to alternately block said first and said second absorption cells,wherein said interlacer is an optical chopper comprising at least one reflective blade angled to direct transmitted IR radiation from one of said optical absorption cells on to both of said optical absorption detectors.
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Abstract
Method and apparatus for detecting, by absorption spectroscopy, an isotopic ratio of a sample, by passing first and second laser beams of different frequencies through the sample. Two IR absorption cells are used, a first containing a reference gas of known isotopic ratio and the second containing a sample of unknown isotopic ratio. An interlacer or reflective chopper may be used so that as the laser frequencies are scanned the absorption of the sample cell and the reference cell are detected alternately. This ensures that the apparatus is continuously calibrated and rejects the baseline noise when phase sensitive detection is used.
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Citations
32 Claims
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1. An infrared, IR spectrometer comprising:
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a first tunable IR laser for providing a first beam at a first wavelength; a second tunable IR laser for providing a second beam at a second wavelength; a first absorption cell arranged to receive both first and second beams; a second absorption cell arranged to receive both first and second beams; a first optical absorption detector arranged to detect said first wavelength; a second optical absorption detector arranged to detect said second wavelength; and an interlacer arranged to alternately block said first and said second absorption cells, wherein said interlacer is an optical chopper comprising at least one reflective blade angled to direct transmitted IR radiation from one of said optical absorption cells on to both of said optical absorption detectors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An infrared, IR, spectrometer comprising:
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a first tunable IR laser for providing a first beam at a first wavelength; a second tunable IR laser for providing second beam at a second wavelength; a first absorption cell arranged to receive both first and second beams; a second absorption cell arranged to receive both first and second beams; a first optical absorption detector arranged to detect said first wavelength; a second optical absorption detector arranged to detect said second wavelength; and an interlacer arranged such that said first and said second absorption cells are alternately switched from receiving said first and said second beams.
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24. A method of isotopic ratio determination comprising the steps of:
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(a) passing a first tunable IR laser beam through a first absorption cell; (b) passing a second tunable IR laser beam through a second absorption cell; (c) detecting the absorption due to a first sample contained within said first cell; and (d) detecting the absorption due to a second sample contained within said second cell such that the isotopic ratio of said second sample is determined; and (e) alternately switching said first and second IR laser beams such that the detecting steps (c) and (d) occur in turn. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32)
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Specification