Two-wavelength phase-shifting interferometer and method
US4832489A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 19, 1986 |
| Grant date | May 23, 1989 |
| Priority date | — |
| Expiry date | Mar 19, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/255
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An improved apparatus and method are described for accurately "reconstructing" steep surface profiles, such as for aspheric surfaces, using improved two-wavelength phase-shifting interferometry, wherein single-wavelength precision is obtained over surfaces having departures of hundreds of visible wavelengths from a reference surface. The disclosed technique avoids cumulative summing of detector errors over a large detector array by computing the "equivalent" phase for each detector independently of the intensities of other detectors. Inaccurate phase data points having an equivalent fringe contrast less than a predetermined threshold are eliminated from data from which contour maps of the aspheric surface are displayed or plotted.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.