US4048859A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Laser accelerometer
Assignee: Boeing North American Inc
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Filing: 1975-10-14
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Granted: 1977-09-20
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Expires: 1995-10-14
Abstract
Abstract An optical element formed of birefringent material is placed in the resonant optical beam path of a gas laser. A proof mass is fixedly attached to the birefringent element to form an integral unit therewith, this unit being contained within the same chamber as the lasing gas. Means are provided to subject the laser beam to a transverse magnetic field which effectively operates to keep the beam separated into E and O rays which are polarized in orthogonal relationship to each other. The proof mass is affixed to the birefringent element so that when such mass is subjected to an acceleration along a predetermined axis, the force arising from this acceleration will be transferred to the birefringent element, there being substantially no transfer of acceleration forces to this element along other axes. The index of refraction of the birefringent material changes in response to the acceleration input received thereby, the index of refraction change seen by each of the cross polarized beams being different. This results in a frequency difference between these two beams that is proportional to the acceleration input and is measured by a detector.
Inventors
- 👤 Gary D. Babcock
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 14:54
CPC Classifications
G; G01; G01P; G01P15/00; G01P15/02; G01P15/08; G01P15/093
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
153 words
A laser accelerometer comprising: a windowless chamber, means for forming a resonant optical laser beam in said chamber, a webbed birefringent sensor element mounted in said chamber, said beam passing through said element, a proof mass integral with said sensor element, a first web portion of said sensor element providing a substantially flexural support for the proof mass along a predetermined acceleration sensing axis and a second web portion thereof perpendicular to said first web portion providing substantially rigid support along axes normal to said predetermined axes, means for subjecting said laser beam to a transverse magnetic field to keep the beam separated into orthogonally polarized components, means for combining said orthogonally related components for heterodyning, and detector means for detecting the difference frequency between the heterodyned components, whereby a difference frequency is developed between said components proportional to the magnitude of the acceleration of said proof mass along said predetermined sensing axis.
Claim 2
Dependent Claim
153 words
A laser accelerometer comprising: a windowless chamber, means for forming a resonant optical laser beam in said chamber, a webbed birefringent sensor element mounted in said chamber, said beam passing through said element, a proof mass integral with said sensor element, a first web portion of said sensor element providing a substantially flexural support for the proof mass along a predetermined acceleration sensing axis and a second web portion thereof perpendicular to said first web portion providing substantially rigid support along axes normal to said predetermined axes, means for subjecting said laser beam to a transverse magnetic field to keep the beam separated into orthogonally polarized components, means for combining said orthogonally related components for heterodyning, and detector means for detecting the difference frequency between the heterodyned components, whereby a difference frequency is developed between said components proportional to the magnitude of the acceleration of said proof mass along said predetermined sensing axis.
Claim 3
Dependent Claim
18 words
The device of claim 1 wherein said laser is a gas laser, said chamber containing the laser gas.
Claim 4
Dependent Claim
19 words
The device of claim 1 the proof mass is joined only to the webbed portion of the sensor element.
Claim 5
Dependent Claim
181 words
A laser accelerometer comprising: a chamber, means for forming a resonant optical laser beam in said chamber, a birefringent sensor element mounted in said chamber, said beam passing through said element, a proof mass integral with said sensor element, said sensor element providing a substantially flexural support for the proof mass along a predetermined acceleration sensing axis and a substantially rigid support along axes normal to said predetermined axes, means for subjecting said laser beam to a transverse magnetic field to keep the beam separated into orthogonally polarized components, means for combining said orthogonally related components for heterodyning, and detector means for detecting the difference frequency between the heterodyned components, whereby a difference frequency is developed between said components proportional to the magnitude of the acceleration of said proof mass along said predetermined sensing axis, said sensor element having a web portion, the proof mass being joined only to the web portion of the sensor element, the web portion being in the form of a cross, the proof mass having slots formed therein which matingly engage the arms of said cross.
Claim 6
Dependent Claim
181 words
A laser accelerometer comprising: a chamber, means for forming a resonant optical laser beam in said chamber, a birefringent sensor element mounted in said chamber, said beam passing through said element, a proof mass integral with said sensor element, said sensor element providing a substantially flexural support for the proof mass along a predetermined acceleration sensing axis and a substantially rigid support along axes normal to said predetermined axes, means for subjecting said laser beam to a transverse magnetic field to keep the beam separated into orthogonally polarized components, means for combining said orthogonally related components for heterodyning, and detector means for detecting the difference frequency between the heterodyned components, whereby a difference frequency is developed between said components proportional to the magnitude of the acceleration of said proof mass along said predetermined sensing axis, said sensor element having a web portion, the proof mass being joined only to the web portion of the sensor element, the web portion being in the form of a cross, the proof mass having slots formed therein which matingly engage the arms of said cross.
Claim 7
Dependent Claim
23 words
The device of claim 4 wherein said sensor element has a second web portion, the laser beam passing through said second web portion.
Claim 8
Dependent Claim
26 words
The device of claim 5 wherein the surface portions of the second web portion are coated with an anti-reflection hard film capable of withstanding plasma bombardment.
Claim 9
Dependent Claim
25 words
The device of claim 4 wherein said proof mass comprises two similar portions joined to each other and to opposite sides of said sensor element.
Claim 10
Dependent Claim
32 words
The device of claim 4 wherein said means for subjecting the laser beam to a transverse magnetic field comprises a plurality of pin magnets mounted along the path of said laser beam.
Claim 11
Dependent Claim
14 words
The device of claim 4 wherein said sensor element is fabricated of fused silica.
Claim 12
Dependent Claim
13 words
The device of claim 9 wherein said sensor element is fabricated of Suprasil.
Claim 13
Dependent Claim
14 words
The device of claim 4 wherein said housing is fabricated of an ultra-low-expansion material.
Claim 14
Dependent Claim
21 words
The device of claim 4 wherein said means for combining said orthogonally polarized components comprises a quarter-wave plate and plane polarizer.
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) | 1980-09-19 | 1981-03-21 | 1981-09-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-09-19 | 1985-03-21 | 1985-09-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-09-19 | 1989-03-21 | 1989-09-20 | $7700.00 | Window Closed / Lapsed |