Method and apparatus for surface topography measurement by spatial-frequency analysis of interferograms
US5398113A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 8, 1993 |
| Grant date | Mar 14, 1995 |
| Priority date | — |
| Expiry date | Feb 8, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B9/0209
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An optical system for measuring the topography of an object includes an interferometer with a multiple-color or white-light source, a mechanical scanning apparatus for varying the optical path difference between the object and a reference surface, a two-dimensional detector array, and digital signal processing apparatus for determining surface height from interference data. Interferograms for each of the detector image points in the field of view are generated simultaneously by scanning the object in a direction approximately perpendicular to the illuminated object surface while recording detector data in digital memory. These recorded interferograms for each image point are then transformed into the spatial frequency domain by Fourier analysis, and the surface height for each corresponding object surface point is obtained by examination of the complex phase as a function of spatial frequency. A complete three-dimensional image of the object surface is then constructed from the height data and corresponding image plane coordinates.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.