US3879988A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical comparator for measuring vibration on a rotating object
Assignee: General Electric Co
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Filing: 1973-12-19
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Granted: 1975-04-29
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Expires: 1993-12-19
Abstract
Abstract An optical comparator is disclosed for measuring small surface vibrations on a rotating object. The comparator employs coherent optical techniques which produce a shift in the optical frequency of a laser beam as a result of surface motion. The comparator uses an optical heterodyne to convert the frequency terms expressive of vibration into a convenient low frequency electrical format. Unique beam path transforming means are disclosed which cause the beam to impinge with a substantially constant angle of incidence upon the same surface element throughout an observation period. By increasing coherence, the apparatus sensitivity is increased to the point where measurement can be made on nonspecular surfaces.
Inventors
- 👤 Gordon B Jacobs
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 10:13
CPC Classifications
G; G01; G01H; G01H1/00; G01H1/003; G01H1/006; G01H9/00
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
121 words
Apparatus for optically measuring a small vibrational motion at the surface of a rotating object, comprising: a. a source of a beam of collimated coherent illumination, b. means to divide the beam into a reference and an analytic beam, c. means to transform the path of said analytic beam in synchronism with said object rotation to cause impingement on said object at a substantially constant angle of incidence throughout a given rotation to increase coherence, d. means to intercept the analytic beam after reflection from said surface element, and e. an optical detector upon which returning reference and analytic beams impinge, said detector having adequate bandwidth to produce a heterodyne between said beams containing Doppler frequency terms indicative of said vibration.
Claim 2
Dependent Claim
121 words
Apparatus for optically measuring a small vibrational motion at the surface of a rotating object, comprising: a. a source of a beam of collimated coherent illumination, b. means to divide the beam into a reference and an analytic beam, c. means to transform the path of said analytic beam in synchronism with said object rotation to cause impingement on said object at a substantially constant angle of incidence throughout a given rotation to increase coherence, d. means to intercept the analytic beam after reflection from said surface element, and e. an optical detector upon which returning reference and analytic beams impinge, said detector having adequate bandwidth to produce a heterodyne between said beams containing Doppler frequency terms indicative of said vibration.
Claim 3
Dependent Claim
32 words
Apparatus as set forth in claim 1 wherein said path transforming means comprises means to cause said analytic beam to rotate substantially in angular synchronism with said object through a given rotation.
Claim 4
Dependent Claim
53 words
Apparatus as set forth in claim 2 wherein said path transforming means comprises means to modify said analytic beam rotation in synchronous fashion to cause the locus of intersection of said beam with the surface of said object to coincide with the arcuate path of a predetermined surface element throughout said given rotation.
Claim 5
Dependent Claim
74 words
ApParatus as set forth in claim 2 wherein said path transforming means comprises: a. a mirror into which said analytic beam is directed, rotating in synchronism with said object to cause beam rotation, and b. a first lens for imaging the rotating beam from said mirror upon said rotating object, disposed to adjust the rate of rotation of the imaged beam into substantial equality with the rate of object rotation through said given rotation.
Claim 6
Dependent Claim
117 words
Apparatus as set forth in claim 4 wherein: a. a second lens is provided for focusing said analytic laser beam on said rotating mirror, b. said rotating mirror is disposed in respect to said first lens so that rotation of said mirror causes said analytic laser beam to traverse successive zones of said first lens, and c. wherein said first lens has appreciable coma to modify the rotation rate of said imaged beam as successive zones are traversed by said input beam to cause the locus of intersection of said analytic beam with the surface of said object to be arcuate, in substantial coincidence with the arcuate path of a predetermined surface element through said given rotation.
Claim 7
Dependent Claim
124 words
Apparatus as set forth in claim 5 wherein: a. said first lens and said mirror, without comatic lens error, produce an arcuate locus having a radius of half the radius of said arcuate path, when said analytic beam is tangential to said arcuate path, b. the axis of said first lens is arranged in relation to the axis of rotation of said object such that said surface element during said given rotation is at a maximum distance from said lens axis at initial and terminal positions and at a minimum distance at mid-position along said angular path; and c. wherein said lens provides adequate negative comatic correction to cause substantial equality in the radii of curvature of said analytic locus and said arcuate path.
Claim 8
Dependent Claim
49 words
Apparatus as set forth in claim 1 wherein: a. said reference beam is directed at a second surface element on said rotating object, and b. said path translating means comprises means to cause said reference beam to rotate substantially in angular synchronism with said object through a given rotation.
Claim 9
Dependent Claim
58 words
Apparatus as set forth in claim 7 wherein: a. said reference beam path translation means comprises means to modify said reference beam rotation in a synchronous fashion to cause the locus of intersection of said reference beam with the surface of said object to coincide with the arcuate path of a predetermined surface element throughout said given rotation.
References Cited (Backward Citations)
US3482436A
Cited
US3782176A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-04-28 | 1978-10-28 | 1979-04-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-28 | 1982-10-28 | 1983-04-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-28 | 1986-10-28 | 1987-04-29 | $7700.00 | Window Closed / Lapsed |