US4112367A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetomer using a thin magnetic film optical waveguide with a.c. modulation and automatic nulling
Assignee: Thales SA
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Filing: 1977-06-14
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Granted: 1978-09-05
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Expires: 1997-06-14
Abstract
Abstract The present invention relates to devices intended to measure magnetic fields, and also known as magnetometers. It consists in using a zeroing method to measure the influence of the Faraday effect of the field being measured, upon a radiated energy beam propagating in guided fashion through a thin film of magnetic material.
Inventors
- 👤 Georges Hepner
- 👤 Bernard Desormiere
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 19:38
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/02; G01R33/032; G01R33/0322
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
288 words
A device for measuring an external magnetic field having a given direction, which comprises: means for generating a first light beam having a linear polarization; a thin film of magnetic material immersed in said external magnetic field and extending along a plane in which said given direction extends, for propagating said first light beam along said given direction in a first guided mode corresponding to said linear polarization and in a second guided mode under the influence of said external magnetic field; the distribution of said light beam between said two modes being dependent on the intensity of said external field; means for coupling said first light beam into said thin film along said given direction; means for extracting from said thin film a second light beam corresponding to the portion of said first beam propagated in said second guided mode; means for applying to said thin film a fixed polarization magnetic field parallel to said plane and perpendicular to said given direction; means for applying to said thin film an AC magnetic field parallel to said given direction and having a given frequency, whereby the intensity of said second light beam is modulated; means for detecting in said second light beam an AC component having said given frequency and a first variable intensity and delivering a control signal representative of said first variable intensity; means for applying to said thin film a variable magnetic field having said given direction, opposed to said external magnetic field, and having a second variable intensity; and means for feedback controlling said second variable intensity under the control of said control signal until said first variable intensity is set to zero said second variable intensity being a measure of the external field.
Claim 2
Independent Claim
288 words
A device for measuring an external magnetic field having a given direction, which comprises: means for generating a first light beam having a linear polarization; a thin film of magnetic material immersed in said external magnetic field and extending along a plane in which said given direction extends, for propagating said first light beam along said given direction in a first guided mode corresponding to said linear polarization and in a second guided mode under the influence of said external magnetic field; the distribution of said light beam between said two modes being dependent on the intensity of said external field; means for coupling said first light beam into said thin film along said given direction; means for extracting from said thin film a second light beam corresponding to the portion of said first beam propagated in said second guided mode; means for applying to said thin film a fixed polarization magnetic field parallel to said plane and perpendicular to said given direction; means for applying to said thin film an AC magnetic field parallel to said given direction and having a given frequency, whereby the intensity of said second light beam is modulated; means for detecting in said second light beam an AC component having said given frequency and a first variable intensity and delivering a control signal representative of said first variable intensity; means for applying to said thin film a variable magnetic field having said given direction, opposed to said external magnetic field, and having a second variable intensity; and means for feedback controlling said second variable intensity under the control of said control signal until said first variable intensity is set to zero said second variable intensity being a measure of the external field.
Claim 3
Dependent Claim
44 words
A device as claimed in claim 1, wherein said thin film is an epitaxial film of gadolinium and gallium substituted yttrium-iron garnet, deposited onto a gadolinium gallium garnet substrate; the light beam being an infra-red beam having a wavelength substantially equal to 1.15 μm.
Claim 4
Dependent Claim
28 words
A device as claimed in claim 2, wherein said coupling means comprise an entry prism and said extracting means comprise an exit prism constituted with double refracting material.
Claim 5
Dependent Claim
35 words
A device as claimed in claim 3, wherein the composition of said thin film is substantially given by the formula Gd 0 .45 Y 2 .55 Fe 4 .2 Ga 0 .8 O 12 .
Claim 6
Dependent Claim
18 words
A device as claimed in claim 4, wherein said thin film has a thickness of substantially 4.4. μm.
Claim 7
Dependent Claim
17 words
A device as claimed in claim 5, wherein said given frequency is substantially equal to 10 kHz.
Claim 8
Dependent Claim
16 words
A device as claimed in claim 6, wherein said means for detecting includes an avalanche diode.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-09-04 | 1982-03-06 | 1982-09-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-09-04 | 1986-03-06 | 1986-09-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-09-04 | 1990-03-06 | 1990-09-05 | $7700.00 | Window Closed / Lapsed |