Method and apparatus for absolute optical measurement of entire surfaces of flats
US5502566A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 13, 1995 |
| Grant date | Mar 26, 1996 |
| Priority date | — |
| Expiry date | Feb 13, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/24
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus for measuring an absolute profile of a flat using an interferometer system that includes an interferometer adapted to support two flats, a detection system, and a computer adapted to compute the OPD (optical path difference) between surface of the two flats, wherein a first flat A! having a first surface and a second flat B! having a second surface are supported in the interferometer, with the second surface facing the first surface. The interferometer system measures the OPDs between the first and second surfaces for each pixel. The first flat A! then is rotated by a number of predetermined angles relative to its initial position and each time the OPDs are measured. The first flat A! is rotated to its initial position or 180.degree. therefrom. A third flat C! having a third surface is substituted for the second flat. The OPDs between the first and third surfaces are measured. The first flat A! is replaced by the second flat, with the second surface facing the third in an orientation mirror imaged to its original orientation. The interferometer system is operated to measure the OPDs. The computer solves first, second, and third equations to obtain the entire …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.