Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1980-06-16
1982-10-12
Punter, William H.
Optics: measuring and testing
By polarized light examination
With light attenuation
356351, 356359, 356360, 356369, G01B 1130, G01B 902
Patent
active
043536506
ABSTRACT:
A method and apparatus is disclosed for testing the deviation of the face of an object from a flat smooth surface using a beam of coherent light of two plane-polarized components, one of a frequency constantly greater than the other by a fixed amount to produce a difference frequency with a constant phase to be used as a reference. The beam also is split into its two components with the separate components directed onto spaced apart points onthe face of the object to be tested for smoothness. The object is rotated on an axis coincident with one component which is directed to the face of the object at the center which constitutes a virtual fixed point. This component also is used as a reference. The other component follows a circular track on the face of the object as the object is rotated. The two components are recombined after reflection to produce a reflected frequency difference of a phase proportional to the difference in path length which is compared with the reference phase to produce a signal proportional to the deviation of the height of the surface along the circular track with respect to the fixed point at the center.
REFERENCES:
patent: 3463924 (1969-08-01), Culshaw et al.
patent: 3472593 (1969-10-01), Drinkwater
patent: 3523735 (1970-08-01), Taylor
patent: 3620593 (1971-11-01), Tackaberry
patent: 3768910 (1973-10-01), Zanoni
patent: 3796495 (1974-03-01), Laub
patent: 3952583 (1976-04-01), Rosati
patent: 4093380 (1978-06-01), White
patent: 4171908 (1979-10-01), Robert et al.
Okoomian, H. J., "A Two-Beam Polarization Technique to Measure Optical Phase", App. Optics, 11/69, pp. 2363-2365.
Besha Richard G.
Clouse, Jr. Clifton E.
Gaither Roger S.
Punter William H.
The United States of America as represented by the United States
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