EP0175358A2
Expired / Lapsed
EP
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Optical sensing equipment
Assignee: Mitsubishi Electric Corp
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Filing: 1985-09-18
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Granted: —
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Expires: 2005-09-18
Abstract
Abstract Optical sensing apparatus for measuring quantities such as a displacement, pressure, electric voltage or field, and magnetic current or field, wherein errors due to fluctuations in the outputs of light sources and transmission losses of optical fibers are eliminated. First and second light sources (1-1, 1-2) are alternately activated, and ratios of their outputs are determined in both cases. Then, the ratio of these two outputs is calculated (calculator 20) to thereby provide a signal representing the quantity being measured. The optical sensing equipment is arranged such that terms affected by fluctuations in the outputs of the light sources and transmission losses in optical fibers (2-1, 2-2) used in the optical sensing equipment cancel out in the divisions providing the three ratios.
Inventors
- 👤 Yoshiaki C/O Mitsubishi Denki K.K. Ida
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 18:56
CPC Classifications
G; G01; G01L; G01L1/00; G01L1/24; G01D; G01D5/00; G01D5/26; G01D5/32; G01D5/34; G01D5/344; G01R; G01R15/00; G01R15/14; G01R15/24; G01R15/247; G01R33/00; G01R33/02; G01R33/032
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
214 words
Optical sensing apparatus characterized by: a first light source (1-1); a first splitter (17-1) receiving light from said first light source; a first photodetector (12) arranged at one output of said first splitter (17-1); a first optical fiber (2-1); a second light source (1-2); a second splitter (17-2) receiving light from said second light source (1-2); a second photodetector (13) arranged at one output of said second splitter; a second optical fiber (2-2); an optical sensor coupled to the other outputs of said first and second splitters (17-1, 17-2) through said first and second optical fibers (2-1, 2-2), respectively, said optical sensor comprising a polarizer (4), a modulator element (5), and fully reflecting mirror (18) arranged in the stated order from said first and second optical fibers; a driving circuit (19) for alternately driving said first and second light sources (1-1, 1-2); a divider (16) for determining a first ratio of outputs of said first and second photodetectors (12, 13) when said first light source is turned on and a second ratio of outputs of said first and second photodetectors when said second light source is turned on; and means (20) for calculat- in g a ratio between said first and second ratios to thereby provide an output proportional to a quantity being measured.
Claim 2
Dependent Claim
214 words
Optical sensing apparatus characterized by: a first light source (1-1); a first splitter (17-1) receiving light from said first light source; a first photodetector (12) arranged at one output of said first splitter (17-1); a first optical fiber (2-1); a second light source (1-2); a second splitter (17-2) receiving light from said second light source (1-2); a second photodetector (13) arranged at one output of said second splitter; a second optical fiber (2-2); an optical sensor coupled to the other outputs of said first and second splitters (17-1, 17-2) through said first and second optical fibers (2-1, 2-2), respectively, said optical sensor comprising a polarizer (4), a modulator element (5), and fully reflecting mirror (18) arranged in the stated order from said first and second optical fibers; a driving circuit (19) for alternately driving said first and second light sources (1-1, 1-2); a divider (16) for determining a first ratio of outputs of said first and second photodetectors (12, 13) when said first light source is turned on and a second ratio of outputs of said first and second photodetectors when said second light source is turned on; and means (20) for calculat- in g a ratio between said first and second ratios to thereby provide an output proportional to a quantity being measured.
Claim 3
Dependent Claim
233 words
Optical sensing apparatus characterized by: a first light source (1-1); a first splitter (17-1) receiving light from said first light source; a first photodetector (12) arranged at one output of said first splitter (17-1); a first optical fiber (2-1); an optical sensor coupled to the other end of said splitter and receiving light therefrom through said first optical fiber (2-1), said optical sensor comprising a polarizer (4), a modulator element (5), and a half-silvered mirror (21) arranged in the stated order from said first optical fiber (2-1); a second optical fiber (2-2); a second splitter (17-2) optically coupled to a surface of said half-silvered mirror (21) opposite said modulator element (5) through said second optical fiber (2-2); a second photodetector (13) arranged at an output of said second splitter (17-2); a second light source (1-2), said second splitter (17-2) receiving light from said second light source (1-2); a driving circuit (19) for alternately driving said first and second light sources (1-2, 2-2); a divider (16) for determining a first ratio of outputs of said first and second photodetectors (12,13) when said first light source (1-2) is turned on and a second ratio of outputs of said first and second photdetectors when said second light source (2-2) is turned on; and means (20) for calculating a ratio between said first and second ratios to thereby provide an output proportional to a quantity being measured.
Claim 4
Dependent Claim
233 words
Optical sensing apparatus characterized by: a first light source (1-1); a first splitter (17-1) receiving light from said first light source; a first photodetector (12) arranged at one output of said first splitter (17-1); a first optical fiber (2-1); an optical sensor coupled to the other end of said splitter and receiving light therefrom through said first optical fiber (2-1), said optical sensor comprising a polarizer (4), a modulator element (5), and a half-silvered mirror (21) arranged in the stated order from said first optical fiber (2-1); a second optical fiber (2-2); a second splitter (17-2) optically coupled to a surface of said half-silvered mirror (21) opposite said modulator element (5) through said second optical fiber (2-2); a second photodetector (13) arranged at an output of said second splitter (17-2); a second light source (1-2), said second splitter (17-2) receiving light from said second light source (1-2); a driving circuit (19) for alternately driving said first and second light sources (1-2, 2-2); a divider (16) for determining a first ratio of outputs of said first and second photodetectors (12,13) when said first light source (1-2) is turned on and a second ratio of outputs of said first and second photdetectors when said second light source (2-2) is turned on; and means (20) for calculating a ratio between said first and second ratios to thereby provide an output proportional to a quantity being measured.
Claim 5
Dependent Claim
47 words
Optical sensing apparatus as claimed in claim 1 or 2, wherein, for measurement of an electric field or voltage, said modulator element (5) comprises a bismuth-germanium-oxide element or a bismuth-silicon-oxide element, and wherein an eighth-wave plate is disposed between said polarizer (4) and said modulator element (5).
Claim 6
Dependent Claim
45 words
Optical sensing apparatus as claimed in claim 1 or 2, wherein, for measurement of a magnetic field or current, said modulator element (5) comprises a bismuth-germanium-oxide element or a bisDuth-siliconoxide element having a length determined so that the plane of polarization is rotated through 45°.
Claim 7
Dependent Claim
49 words
Optical sensing apparatus as claimed in claim 1 or 2, wherein, for measurement of a pressure or displacement, said modulator element (5) comprises a body of material having a photoelastic effect, and wherein, an eighth wave phase plate is inserted between said polarizer (4) and said modulator element (5).
Claim 8
Dependent Claim
22 words
Optical sensing apparatus as claimed in claim 1 or 2, wherein said modulator element comprises a Faraday element or a Pcckels element.
Claim 9
Dependent Claim
18 words
Optical sensing apparatus as claimed in claim 1 or 2, wherein said splitter comprises a polarizing beam splitter.
References Cited (Backward Citations)
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