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Interferometric apparatus for ultra-high precision displacement measurementA high-precision heterodyne interferometer measures relative displacement by creating a thermally-insensitive system generally not subject to polarization leakage. By using first and second light beams separated by a small frequency difference (.DELTA.f), beams of light at the first frequency (f.sub.0) are reflected by co-axial mirrors, the first mirror of which has a central aperture through which the light is transmitted to and reflected by the second mirror. Prior to detection, the light beams from the two mirrors are combined with light of the second and slightly different frequency. The combined light beams are separated according to the light from the mirrors. The change in phase (.DELTA..phi.) with respect to the two signals is proportional to the change in distance of Fiducial B by a factor of wavelength (.lambda.) divided by 4.pi. (.DELTA.L=.lambda..DELTA..phi.1/(4.pi.)). In a second embodiment, a polarizing beam splitting system can be used.
Document ID
20080007032
Acquisition Source
Headquarters
Document Type
Other - Patent
Authors
Zhao, Feng
Date Acquired
August 24, 2013
Publication Date
March 23, 2004
Subject Category
Optics
Report/Patent Number
Patent Number: US-PATENT-6,710,880
Patent Application Number: US-PATENT-APPL-SN-950237
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Patent
US-PATENT-6,710,880
Patent Application
US-PATENT-APPL-SN-950237
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