Single-channel gas concentration measurement method and apparatus using a short-resonator Fabry-Perot interferometer
First Claim
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1. A single-channel infrared gas concentration measurement method comprising the following steps:
- generating a measuring signal by means of a radiant source;
directing the measuring signal to a measurement object containing a gas mixture to be measured;
bandpass filtering the measuring signal after being directed to the measurement object by implementing a single electrostatically tunable, short-resonator Fabry-Perot interferometer fabricated by surface micromachining techniques and having upper and lower resonator mirrors with a distance between said mirrors being equal to n μ
/2 where n is from 1 to 3, said interferometer further having an aperture integrally provided in an interferometer structure and located adjacent to a side of said lower mirror which is opposite said upper mirror, said aperture being filled with silicon substrate, said bandpass filtering using at least two passband wavelengths; and
detecting the measuring signal which has been filtered by means of a detector.
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Abstract
A single-channel gas concentration measurement method and apparatus. According to the method, a radiant source is employed to generate a measuring signal, the measuring signal is subsequently directed to a measurement object containing a gas mixture to be measured, the measuring signal is subsequently bandpass filtered using at least two passband wavelengths, and the filtered measuring signals are detected by a detector. According to the invention, the bandpass filtering step is implemented by a single electrostatically tunable, short-resonator Fabry-Perot interferometer.
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Citations
14 Claims
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1. A single-channel infrared gas concentration measurement method comprising the following steps:
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generating a measuring signal by means of a radiant source; directing the measuring signal to a measurement object containing a gas mixture to be measured; bandpass filtering the measuring signal after being directed to the measurement object by implementing a single electrostatically tunable, short-resonator Fabry-Perot interferometer fabricated by surface micromachining techniques and having upper and lower resonator mirrors with a distance between said mirrors being equal to n μ
/2 where n is from 1 to 3, said interferometer further having an aperture integrally provided in an interferometer structure and located adjacent to a side of said lower mirror which is opposite said upper mirror, said aperture being filled with silicon substrate, said bandpass filtering using at least two passband wavelengths; anddetecting the measuring signal which has been filtered by means of a detector. - View Dependent Claims (2, 3, 4, 5)
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6. A single-channel infrared gas concentration measurement apparatus, comprising:
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a measuring a radiant source for generating a measuring signal; a measurement object containing a gas mixture to be measured and through which said measuring signal is sent; a variable bandpass filter for bandpass filtering of the measuring signal on at least two passband wavelengths, said bandpass filter being implemented by means of a single electrostatically tunable, short-resonator Fabry-Perot interferometer fabricated by surface micromachining techniques and having upper and lower resonator mirrors with a distance between said mirrors being equal to n λ
/2 where n is from 1 to 3, said interferometer further having an aperture integrally provided in an interferometer structure and located adjacent to a side of said lower mirror which is opposite said upper mirror, said aperture being filled with silicon substrate; anda detector suited for detecting said filtered measuring signals. - View Dependent Claims (7, 8)
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9. An electrically tunable short-resonator Fabry-Perot interferometer fabricated by surface micromachining techniques for infrared gas concentration measurement, said interferometer comprising:
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upper and lower essentially parallel, adjacently aligned, semi-transmissive mirrors spaced at a distance (d) which is designed proportional to a center wavelength (λ
) of the interferometer passband according to the formula;
space="preserve" listing-type="equation">d=nλ
/2,where n is an integer from 1 to 3 indicating an interferometer order number, said lower mirror having first and second opposite sides, said upper mirror being located closest to said first side of said lower mirror; control means for modulating the distance (d) between said resonator mirrors; and an aperture integrally provided in an interferometer structure and located closest to said second side of said lower mirror, said aperture being filled with silicon substrate. - View Dependent Claims (10, 11, 12, 13, 14)
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Specification