Interferometer system with two wavelengths, and lithographic apparatus provided with such a system
US6122058A · kind A · utility
42Cited by
10References
24Claims
0Family size
Assignee
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Key dates
| Filing date | Jun 24, 1998 |
| Grant date | Sep 19, 2000 |
| Priority date | — |
| Expiry date | Jun 24, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B2290/70
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
In an interferometer system, variations of the refractive index in the medium traversed by the measuring beam (123) can be detected by using two measuring beams (123, 125) having wavelengths which differ by a factor of three. For this choice of the wavelength ratio, the interference filters of the polarization elements, such as the beam splitter (127), the .lambda./4 plates (130, 131) and the antireflection coatings can be manufactured relatively easily, and the detection accuracy is increased.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.