US3849003A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Interferometer apparatus for measuring the roughness of a surface
Assignee: US Philips Corp
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Filing: 1973-04-06
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Granted: 1974-11-19
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Expires: 1993-04-06
Abstract
Abstract An apparatus for measuring the roughness of a surface is described which includes an optical system by means of which two images of the surface which have a mutual phase difference and displacement are superposed on one another. It is disserted that for this purpose the phase difference is produced between two sub-beams polarized in directions at right angles to one another by means of an electro-optical modulator, the displacement being effected in an interferometer which discriminates in respect of direction of polarisation. It is set forth that the interferometer may include the series arrangement of the two Wollaston prisms which produce opposite angle splittings between cross-polarized beams of radiation which enter the series arrangement.
Inventors
- 👤 C Velzel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:10
CPC Classifications
G; G01; G01B; G01B9/00; G01B9/02; G01B11/00; G01B11/30; G01B11/303; G01B2290/00; G01B2290/70
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
143 words
An apparatus for measuring the roughness of a surface, comprising an electro-optical modulator having electrical terminals for receiving a periodic electrical signal, means for projecting substantially monochromatic radiation through the electro-optical modulator, the electro-optical modulator thereby providing two aligned orthogonally polarized sub-beams having a periodically varying phase difference, an interferometer in the path of the sub-beams from the electro-optical modulator for spatially displacing the sub-beams in accordance with the direction of polarization, means in the interferometer for continuously varying the spatial displacement of the subbeams, means for superimposing the initially displaced sub-beams on the surface to be measured and for directing reflected radiation from the surface back to the interferometer wherein the spatial displacement between the sub-beams is removed, an analyzer in the path of the re-combined reflected sub-beams, and a photo detector in the path of the beams passing through the analyzer.
Claim 2
Independent Claim
143 words
An apparatus for measuring the roughness of a surface, comprising an electro-optical modulator having electrical terminals for receiving a periodic electrical signal, means for projecting substantially monochromatic radiation through the electro-optical modulator, the electro-optical modulator thereby providing two aligned orthogonally polarized sub-beams having a periodically varying phase difference, an interferometer in the path of the sub-beams from the electro-optical modulator for spatially displacing the sub-beams in accordance with the direction of polarization, means in the interferometer for continuously varying the spatial displacement of the subbeams, means for superimposing the initially displaced sub-beams on the surface to be measured and for directing reflected radiation from the surface back to the interferometer wherein the spatial displacement between the sub-beams is removed, an analyzer in the path of the re-combined reflected sub-beams, and a photo detector in the path of the beams passing through the analyzer.
Claim 3
Dependent Claim
29 words
An apparatus as claimed in claim 1, wherein the interferometer comprises two serially arranged Wollaston prisms for producing opposite angle-splittings between the cross-polarized beams of radiation entering the interferometer.
Claim 4
Dependent Claim
119 words
An apparatus as claimed in claim 1, wherein the interferometer comprises a beam-splitting mirror in the path of the sub-beams from the modulator, two plane mirrors inclined at equal and opposite angles to the plane of the beam-splitting mirror, the beam-splitting mirror receiving the substantially monochromatic radiation, splitting it into partial beams and directing each partial beam to a separate one of the two plane mirrors, the partial beams thereby propagating in opposite directions along the same internal path from the beam-splitting mirror to each plane mirror and back to the beam-splitting mirror, a polarizer in the internal path of both partial beams, and a half-wave plate serially arranged with the polarizer within the internal path of the interferometer.
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) | 1977-11-18 | 1978-05-20 | 1978-11-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-18 | 1982-05-20 | 1982-11-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-18 | 1986-05-20 | 1986-11-19 | $7700.00 | Window Closed / Lapsed |