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US4900918A
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Resonant fiber optic accelerometer with noise reduction using a closed loop feedback to vary pathlength
Assignee: Honeywell International Inc
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Filing: 1987-08-06
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Granted: 1990-02-13
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Expires: 2007-08-06
Abstract
Abstract A pair of resonant optical cavities are used to measure shifts in length of a beam which deflects under acceleration. One end of each optical cavity is highly reflective and the other end partially reflective, thus permitting resonating light to exit the resonators. The light outputs of the two resonators is combined and the resultent beat frequency is used to detect deflections of the beam.
Inventors
- 👤 Kevin M. Killian
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 05:14
CPC Classifications
G; G01; G01P; G01P15/00; G01P15/02; G01P15/08; G01P15/093; G01D; G01D5/00; G01D5/12; G01D5/243
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
165 words
Accelerometer is which a proof mass is suspended by a cantilever beam, and deflection of the beam is proportional to acceleration, characterized by: two resonant light paths, the light paths being rendered unequal in length by the deflection of the beam; a common light source connected to the light paths; a means to obtain optical outputs representative of light resonating in each of the light paths; means to merge the optical outputs; photodetection means responsive to the merged optical outputs and sensitive to changes in the character of light as a result of said unequal path lengths; and a feedback loop including first means in one of the light paths and second means connected to the first means and to the photodetection means, said first means varying the length of the one light path to equalize the lengths of the two light paths which have been rendered unequal by the acceleration, said second means applying a signal to the first means commensurate with said acceleration.
Claim 2
Dependent Claim
165 words
Accelerometer is which a proof mass is suspended by a cantilever beam, and deflection of the beam is proportional to acceleration, characterized by: two resonant light paths, the light paths being rendered unequal in length by the deflection of the beam; a common light source connected to the light paths; a means to obtain optical outputs representative of light resonating in each of the light paths; means to merge the optical outputs; photodetection means responsive to the merged optical outputs and sensitive to changes in the character of light as a result of said unequal path lengths; and a feedback loop including first means in one of the light paths and second means connected to the first means and to the photodetection means, said first means varying the length of the one light path to equalize the lengths of the two light paths which have been rendered unequal by the acceleration, said second means applying a signal to the first means commensurate with said acceleration.
Claim 3
Dependent Claim
36 words
Accelerometer as described in claim 1, further characterized by: each of said light paths including at least two reflective surfaces, the distance between the reflective surfaces being the equal to resonant length of that light path.
Claim 4
Dependent Claim
38 words
Accelerometer as described in claim 2, further characterized by: means to transmit a portion of light from within each resonant light path to outside of the resonant light path so as to be provided to the photodetection means.
Claim 5
Dependent Claim
25 words
Accelerometer as described in claim 3, further characterized by: the light source being connected to each of the light paths through the means to transmit.
Claim 6
Dependent Claim
35 words
Accelerometer as described in claim 3, further characterized by: each of the light paths having a partially reflective mirror as one of the reflective surfaces; and the means to transmit including said partially reflective mirror.
Claim 7
Dependent Claim
25 words
Accelerometer as described in claim 4, further characterized by: the light source being connected to each of the light paths through the means to transmit.
Claim 8
Dependent Claim
27 words
Accelerometer as described in claim 5 further characterized by: a phase modulator in at least one of the light paths; and means to control the phase modulator.
Claim 9
Dependent Claim
40 words
Accelerometer as described in claim 7, further characterized by: the means to control the phase modulator responsive to the photodetection means in order to maintain a fixed frequency relationship between said light paths by phase modulating said one light path.
Claim 10
Dependent Claim
33 words
Accelerometer as described in claim 8, further characterized by: means to sense a reversal of phase in the character of light, the sensed reversal of phase providing as indication of direction of acceleration.
Claim 11
Dependent Claim
33 words
Accelerometer as described in claim 8, further characterized by: said unequal light paths being sufficient to bias a beat frequency, generated by the merged light outputs, beyond an anticipated range of sensed acceleration.
Claim 12
Dependent Claim
35 words
Accelerometer as described in claim 8, further characterized by: a further sensor sensing the same deflection as said plurality of light paths, the further sensor resolving ambiguities with respect to opposite deflections of the beam.
Claim 13
Dependent Claim
16 words
Accelerometer as described in claim 9, further characterized by: the further sensor being a strain gauge.
References Cited (Backward Citations)
US4454418A
Cited
US4613752A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-02-12 | 1993-08-14 | 1994-02-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-02-12 | 1997-08-14 | 1998-02-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-02-12 | 2001-08-14 | 2002-02-13 | $7700.00 | Window Closed / Lapsed |