Interferometric methods and systems using low coherence illumination
US5953124A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 19, 1998 |
| Grant date | Sep 14, 1999 |
| Priority date | — |
| Expiry date | Jan 19, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/2441
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Low coherence illumination is used in interferometric methods and systems which exhibit improved precision and flexibility. According to a first aspect of the invention, both a phase shifting interferometry (PSI) analysis and a scanning white light interferometry (SWLI) analysis are applied to a single 3D interferogram. This allows the precision of PSI to be achieved without being limited by the 2.pi. phase ambiguity constraint. According to another aspect of the invention, a position of a contrast peak of a broad-band 3D interferogram is located by calculating a single Fourier transform coefficient, using the Fourier transform coefficient to determine an analytic equation which corresponds to the derivative of the visibility function, and locating the peak contrast position by setting the derivative equal to zero. The use of analytic equation contrast peak detection improves accuracy and computational efficiency. According to another aspect of the invention, a PSI analysis is applied to a broad-band 3D interferogram generated using a low coherence illumination source. The ability to perform a PSI analysis on a broad-band 3D interferogram promotes flexibility because it allows for …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.