EP0608049A2
Expired / Lapsed
EP
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Single-channel gas concentration measurement method and apparatus
Assignee: Vaisala Oy
•
Filing: 1994-01-06
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Granted: —
•
Expires: 2014-01-06
Abstract
Abstract The invention concerns a single-channel gas concentration measurement method and apparatus. According to the method, a radiant source (1) is employed to generate a measuring signal, the measuring signal is subsequently directed to a measurement object (3) 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 means of a detector (9). According to the invention, the bandpass filtering step is implemented by means of a single electrically tunable, short-resonator Fabry-Perot interferometer (7).
Inventors
- 👤 Yrjö Koskinen
- 👤 Ari Lehto
- 👤 Simo Tammela
- 👤 Martti Blomberg
- 👤 Markku Orpana
- 👤 Altti Torkkeli
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 22:25
CPC Classifications
G; G01; G01J; G01J3/00; G01J3/12; G01J3/26; G01N; G01N21/00; G01N21/17; G01N21/25; G01N21/31; G01N21/35; G01N21/3504; G02; G02B; G02B26/00; G02B26/02; G01J2003/1226; G01J2003/1247
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
88 words
A single-channel gas concentration measurement method in which - a measuring signal is generated by means of a radiant source (1), - the measuring signal is directed to a measurement object (3) 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 means of a detector (9), characterized in that - the bandpass filtering step is implemented by means of a single electrically tunable, short-resonator Fabry-Perot interferometer (7).
Claim 2
Dependent Claim
88 words
A single-channel gas concentration measurement method in which - a measuring signal is generated by means of a radiant source (1), - the measuring signal is directed to a measurement object (3) 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 means of a detector (9), characterized in that - the bandpass filtering step is implemented by means of a single electrically tunable, short-resonator Fabry-Perot interferometer (7).
Claim 3
Dependent Claim
19 words
A method as defined in claim 1, characterized in that the concentration of carbon dioxide or monoxide is measured.
Claim 4
Dependent Claim
21 words
A method as defined in claim 1, characterized in that the radiant source (1) employed is an electrically modulatable radiant source.
Claim 5
Dependent Claim
44 words
A method as defined in claim 1, characterized in that such a Fabry-Perot interferometer (5) is employed which is fabricated by surface micromachining techniques onto a silicon substrate so that one of the resonator mirrors is movable by means of a modulating electric field.
Claim 6
Dependent Claim
29 words
A method as defined in claim 1, characterized in that the measuring signal is subjected to filtering with a cut-offfilter prior to taking said signal to the detector (9).
Claim 7
Dependent Claim
83 words
A single-channel gas concentration measurement apparatus comprising - a radiant source (1) for generating a measuring signal, - a measurement object (3) containing a gas mixture to be measured, - at least two bandpass filters (5) for the bandpass filtering of the measuring signal on at least two passband wavelengths, and - a detector (9) suited for detecting said filtered measuring signals, characterized in that - said bandpass filters (5) are implemented by means of a single electrically tunable, short-resonator Fabry-Perot interferometer (7).
Claim 8
Dependent Claim
83 words
A single-channel gas concentration measurement apparatus comprising - a radiant source (1) for generating a measuring signal, - a measurement object (3) containing a gas mixture to be measured, - at least two bandpass filters (5) for the bandpass filtering of the measuring signal on at least two passband wavelengths, and - a detector (9) suited for detecting said filtered measuring signals, characterized in that - said bandpass filters (5) are implemented by means of a single electrically tunable, short-resonator Fabry-Perot interferometer (7).
Claim 9
Dependent Claim
20 words
An apparatus as defined in claim 6, characterized in that said radiant source (1) is an electrically modulatable radiant source.
Claim 10
Dependent Claim
26 words
An apparatus as defined in claim 6, characterized in that said measurement apparatus incorporates a cut-off filter on the signal path prior to said detector (9).
Claim 11
Dependent Claim
115 words
An electrically tunable Fabry-Perot interferometer fabricated by surface micromachining techniques for gas concentration measurement, said interferometer comprising - two essentially parallel, adjacently aligned, semi-transmissive mirrors (21, 22) spaced at a distance (d) which is designed proportional to the center wavelength ('A) of the interferometer passband according to the formula: d = nλ/2, where n is an integer indicating the interferometer order number, and - control means (16) for modulating the distance (d) between said resonator mirrors, characterized in that - the interferometer order number (n) is 1 3, whereby the interferometer is defined as a short-cavity interferometer, and - the interferometer is provided with an aperture (17) which is fabricated integral with the interferometer structure.
Claim 12
Dependent Claim
115 words
An electrically tunable Fabry-Perot interferometer fabricated by surface micromachining techniques for gas concentration measurement, said interferometer comprising - two essentially parallel, adjacently aligned, semi-transmissive mirrors (21, 22) spaced at a distance (d) which is designed proportional to the center wavelength ('A) of the interferometer passband according to the formula: d = nλ/2, where n is an integer indicating the interferometer order number, and - control means (16) for modulating the distance (d) between said resonator mirrors, characterized in that - the interferometer order number (n) is 1 3, whereby the interferometer is defined as a short-cavity interferometer, and - the interferometer is provided with an aperture (17) which is fabricated integral with the interferometer structure.
Claim 13
Dependent Claim
17 words
An interferometer as defined in claim 9, characterized in that said aperture (17) is fabricated from metal.
Claim 14
Dependent Claim
22 words
An interferometer as defined in claim 9, characterized in that said aperture (17) is fabricated by doping into the silicon substrate (11).
Claim 15
Dependent Claim
21 words
An interferometer as defined in claim 9, characterized in that said aperture (17) is fabricated by doping into a polycrystalline membrane.
Claim 16
Dependent Claim
39 words
An electrically tunable, surface micromechani- cally fabricated Fabry-Perot interferometer as defined in claim 9, characterized in that said interferometer incorporates an integrated absorbing element (18) to the end of preventing transmission of radiation at undesirable wavelengths through said interferometer.
Claim 17
Dependent Claim
19 words
An interferometer as defined in claim 9, characterized in that the thickness of said absorbing element (18) is X/2.
Claim 18
Dependent Claim
40 words
An electrically tunable, surface micromechani- cally fabricated Fabry-Perot interferometer as defined in claim 9, characterized in that said interferometer incorporates holes (14) at the rim of the interferometer resonator upper mirror (20) for etching-away material from inside said resonator cavity.
References Cited (Backward Citations)
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