US4643576A
Expired / Lapsed
US
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Fringe scanning shearing interferometer
Assignee: Ricoh Co Ltd
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Filing: 1985-04-18
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Granted: 1987-02-17
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Expires: 2005-04-18
Abstract
Abstract A fringe scanning shearing interferometer includes a converter lens for converting a wavefront reflected by an object under test illuminated with light into an approximately parallel wavefront, a beam splitter for dividing the approximately parallel wavefront into first and second wavefronts travelling in two directions, a pair of first and second prisms disposed respectively adjacent to the beam splitter in equally spaced relation thereto, a displacement mechanism for displacing the first prism in a direction normal to the direction in which the first wavefront falls on the first prism, a shearing device for slightly displacing the second prism in the same direction as that in which the second wavefront falls on the second prism, a photodetector, and a focusing lens for focusing the first and second wavefronts having passed respectively through the first and second prism, on the photodetector to produce interference fringes thereon.
Inventors
- 👤 Toshio Kanoh
- 👤 Taira Kouchiwa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 09:23
CPC Classifications
G; G01; G01B; G01B9/00; G01B9/02; G01B9/02097; G01B9/02098; G01J; G01J9/00; G01J9/02; G01J9/0215; G01M; G01M11/00; G01M11/005
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
190 words
A fringe scanning shearing interferometer comprising: (a) converter means for converting a wavefront reflected by an object under test, illuminated with light, into an approximately parallel wavefront; (b) splitter means for dividing said approximately parallel wavefront into first and second wavefronts travelling in two directions; (c) a pair of first and second optical path changing means which conduct the first and second wavefronts, respectively, and are disposed respectively adjacent to said splitter means in equally spaced relation thereto; (d) displacement means for displacing said first optical path changing means in a direction normal to the direction in which said first wavefront falls on said first optical path changing means; (e) shearing means for slightly displacing said second optical path changing means in the same direction as that in which second wavefront falls on said second optical path changing means; (f) a photodetector; and (g) a focusing lens for focusing said first and second wavefronts, which have passed respectively through said first and second optical path changing means and have been directed thereby so that they can be focused by said focusing lens, on said photodetector to produce interference fringes thereon.
Claim 2
Dependent Claim
190 words
A fringe scanning shearing interferometer comprising: (a) converter means for converting a wavefront reflected by an object under test, illuminated with light, into an approximately parallel wavefront; (b) splitter means for dividing said approximately parallel wavefront into first and second wavefronts travelling in two directions; (c) a pair of first and second optical path changing means which conduct the first and second wavefronts, respectively, and are disposed respectively adjacent to said splitter means in equally spaced relation thereto; (d) displacement means for displacing said first optical path changing means in a direction normal to the direction in which said first wavefront falls on said first optical path changing means; (e) shearing means for slightly displacing said second optical path changing means in the same direction as that in which second wavefront falls on said second optical path changing means; (f) a photodetector; and (g) a focusing lens for focusing said first and second wavefronts, which have passed respectively through said first and second optical path changing means and have been directed thereby so that they can be focused by said focusing lens, on said photodetector to produce interference fringes thereon.
Claim 3
Dependent Claim
31 words
A fringe scanning shearing interferometer according to claim 1, wherein said object under test has a surface which comprises one of a flat surface, a spherical surface, and an aspherical surface.
Claim 4
Dependent Claim
34 words
A fringe scanning shearing interferometer according to claim 1, wherein said object under test comprises an optical device measured for one of a wavefront aberration, a degree of eccentricity, and a focal length thereof.
Claim 5
Dependent Claim
19 words
A fringe scanning shearing interferometer according to claim 1, wherein said light falling on said object comprises coherent light.
Claim 6
Dependent Claim
17 words
A fringe scanning shearing interferometer according to claim 4, wherein said coherent light comprises a laser beam.
Claim 7
Dependent Claim
33 words
A fringe scanning shearing interferometer according to claim 1, wherein said converting means comprises a converter lens for converting a parallel light beam into a spherical wave lying on a reference spherical surface.
Claim 8
Dependent Claim
46 words
A fringe scanning shearing interferometer according to claim 6, wherein said reference spherical surface has a radius equal to a distance from the focal point of said converter lens to the vertex of a curved surface under test of said object on an optical axis thereof.
Claim 9
Dependent Claim
35 words
A fringe scanning shearing interferometer according to claim 1, wherein said splitter means comprises a beam splitter having a mirror surface inclined 45° with respect to the direction in which said approximately parallel wavefront travels.
Claim 10
Dependent Claim
23 words
A fringe scanning shearing interferometer according to claim 1, wherein each of first and second optical path changing means comprises a right-angled prism.
Claim 11
Dependent Claim
34 words
A fringe scanning shearing interferometer according to claim 9, wherein said right-angled prism has reflecting roof surfaces disposed to reflect back one of said first and second wavefronts which fall on the right-angled prism.
Claim 12
Dependent Claim
53 words
A fringe scanning shearing interferometer according to claim 9, wherein said displacement means comprises a step motor having a shaft, a screw shaft coupled coaxially to said shaft of the step motor, and a frame threaded over said screw shaft and connected to said right-angled prism of said first optical path changing means.
Claim 13
Dependent Claim
17 words
A fringe scanning shearing interferometer according to claim 9, wherein said displacement means comprises a piezoelectric device.
Claim 14
Dependent Claim
29 words
A fringe scanning shearing interferometer according to claim 9, wherein said shearing means comprises a piezoelectric device coupled to said right-angled prism of said second optical path changing means.
Claim 15
Dependent Claim
52 words
A fringe scanning shearing interferometer according to claim 1, wherein each of first and second optical path changing means comprises a conical corner-cube prism having three roof angles and disposed to reflect back one of said first and second wavefronts along an axis precisely parallel to the incident axis of the wavefront.
Claim 16
Dependent Claim
106 words
A fringe scanning shearing interferometer according to claim 14, wherein said displacement means comprises a pair of step motors having respective shafts, a pair of screw shafts coupled coaxially to said shafts of the step motors and extending at at a right angle with respect to each other, and a pair of frames threaded over said screw shafts and connected to said corner-cube prism of said first optical path changing means, whereby said first optical path changing means can be displaced in two orthogonal directions lying in a plane normal to the direction in which said first wavefront falls on said first optical path changing means.
Claim 17
Dependent Claim
29 words
A fringe scanning shearing interferometer according to claim 14, wherein said displacement means comprises a piezoelectric device coupled to said corner-cube prism of said first optical path changing means.
Claim 18
Dependent Claim
53 words
A fringe scanning shearing interferometer according to claim 14, wherein said shearing means comprises a step motor having a shaft, a screw shaft coupled coaxially to said shaft of the step motor, and a frame threaded over said screw shaft and connected to said corner-cube prism of said second optical path changing means.
Claim 19
Dependent Claim
29 words
A fringe scanning shearing interferometer according to claim 14, wherein said shearing means comprises a piezoelectric device coupled to said corner-cube prism of said second optical path changing means.
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) | 1990-02-16 | 1990-08-18 | 1991-02-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-02-16 | 1994-08-18 | 1995-02-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-02-16 | 1998-08-18 | 1999-02-17 | $7700.00 | Window Closed / Lapsed |