Patent US5377295A successfully refreshed from Google Patents.
Patent US3833301A successfully refreshed from Google Patents.
US3833301A
Expired / Lapsed
US
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Testing of spherical surfaces by holographic interference
Assignee: Rank Organization Ltd
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Filing: 1973-05-10
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Granted: 1974-09-03
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Expires: 1993-05-10
Abstract
Abstract In place of earlier known sphericity testing techniques using accurate reference surfaces which are compared with a surface under test, this invention provides an absolute test of sphericity by making use, in effect, of the spherical wavefronts emanting from or converging to a point. A hologram plate is illuminated with coherent light from a laser to establish a first beam which forms a virtual image at the same point as that at which a beam illuminating the surface under test is focused, the illuminating beam being reflected at the surface and forming with the first beam observable interference fringes indicative of departures of the surface under test from true sphericity.
Inventors
- 👤 W Moore
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 16:02
CPC Classifications
G; G01; G01B; G01B9/00; G01B9/02; G01B9/021; G02; G02B; G02B5/00; G02B5/32; Y; Y10; Y10S; Y10S359/00; Y10S359/90; Y10S359/902
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
145 words
A method of testing the sphericity of a nominally spherical surface of an object, comprising illuminating a first hologram with coherent light from a laser source to establish a first beam of light diverging from a point, illuminating a second hologram with coherent light from the same laser source, the second hologram being so formed and arranged that it establishes a second beam of light diverging from a virtual image coinciding with said point, positioning the object under test in the first beam with its centre of curvature at least approximately coinciding with said point, and observing interference fringes between light derived from the first beam in the presence of the object under test, and the said second beam of light derived from the illumination of the second hologram, said fringes being indicative of departures of the said surface of the object from true sphericity.
Claim 2
Independent Claim
145 words
A method of testing the sphericity of a nominally spherical surface of an object, comprising illuminating a first hologram with coherent light from a laser source to establish a first beam of light diverging from a point, illuminating a second hologram with coherent light from the same laser source, the second hologram being so formed and arranged that it establishes a second beam of light diverging from a virtual image coinciding with said point, positioning the object under test in the first beam with its centre of curvature at least approximately coinciding with said point, and observing interference fringes between light derived from the first beam in the presence of the object under test, and the said second beam of light derived from the illumination of the second hologram, said fringes being indicative of departures of the said surface of the object from true sphericity.
Claim 3
Dependent Claim
47 words
The method defined in claim 1, including the preliminary step of forming said second hologram by exposing a photographic plate to two interfering coherent light beams, one of which is a divergent beam diverging from said point, and subsequently processing said plate to form the second hologram.
Claim 4
Dependent Claim
58 words
The method defined in claim 1, including the preliminary step of forming said first hologram by exposing a photographic plate to light from the said laser source and to a pencil of light, also derived from said laser source, which diverges from a point focus at said point, and subsequently processing said plate to form the first hologram.
Claim 5
Dependent Claim
73 words
The method defined in claim 2, including the preliminary step of forming said first hologram by exposing a photographic plate to light from the said laser and to a pencil of light, also derived from said laser source, which diverges from a point focus at said point, and subsequently processing said plate to form the first holograM, and wherein the coherent light which illuminates said second hologram passes first through the first hologram.
Claim 6
Dependent Claim
146 words
Apparatus for testing the sphericity of a nominally spherical surface of an object, comprising: a first hologram; a laser source of coherent light; means for illuminating said first hologram with a parallel beam of coherent light from said laser source; said first hologram establishing when so illuminated a first beam diverging from a point; means mounting the object under test with said first beam incident on said surface thereof and with the centre of said surface at least approximately concentric with said point; a second hologram; means illuminating said second hologram with said coherent light from said laser source; said second hologram establishing when so illuminated a second beam diverging from a virtual image coinciding with said point, and means for observing interference fringes formed as a result of interference between the first beam in the presence of the object under test and the second beam.
Claim 7
Dependent Claim
146 words
Apparatus for testing the sphericity of a nominally spherical surface of an object, comprising: a first hologram; a laser source of coherent light; means for illuminating said first hologram with a parallel beam of coherent light from said laser source; said first hologram establishing when so illuminated a first beam diverging from a point; means mounting the object under test with said first beam incident on said surface thereof and with the centre of said surface at least approximately concentric with said point; a second hologram; means illuminating said second hologram with said coherent light from said laser source; said second hologram establishing when so illuminated a second beam diverging from a virtual image coinciding with said point, and means for observing interference fringes formed as a result of interference between the first beam in the presence of the object under test and the second beam.
Claim 8
Dependent Claim
49 words
The apparatus defined in claim 5, including reflecting elements in the path of the parallel coherent light beam after it has passed through the first hologram, said reflecting elements turning said coherent light beam through 180* prior to the illumination by said coherent light beam of the second hologram.
Claim 9
Dependent Claim
84 words
The apparatus defined in claim 5, including a beam splitting element in the path of the coherent light beam from the laser for obtaining a further coherent light beam, objective lens means in the path of said further coherent light beam for focusing said further coherent light beam to said point to diverge therefrom for the purpose of exposing a photographic plate illuminated by the first coherent light beam and by the said divergent coherent light beam in the formation of the first hologram.
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) | 1977-09-02 | 1978-03-04 | 1978-09-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-09-02 | 1982-03-04 | 1982-09-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-09-02 | 1986-03-04 | 1986-09-03 | $7700.00 | Window Closed / Lapsed |