Phase shifting interferometer and method for surface topography measurement
US5473434A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 16, 1994 |
| Grant date | Dec 5, 1995 |
| Priority date | — |
| Expiry date | May 16, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B9/02087
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A system for measuring surface topography with notably decreased sensitivity to errors in phase and phase interval calibration and to the presence of low-frequency vibration during data acquisition includes an optical interferometer for developing interference data from the surface to be profiled, an electronic imaging system or camera for receiving the interference data, an arrangement for variably adjusting the reference phase of the interferometer illumination, and a digital signal processing device or computer for determining surface height from the interference data. A sequence of seven intensity images are detected by the imaging system and stored electronically. The intensity images correspond to interference patterns for seven different reference phase values spaced at intervals of approximately .pi./2. The images are processed by the computer so as to recover the surface topography. The invention differs substantially from the prior art in that the phase shifts need not be perfectly exact or repeatable, and neither is it necessary to completely eliminate low-frequency mechanical vibrations from the optical system during data acquisition. An alternative embodiment of the in…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.