System and method for detecting the relative positional deviation between diffraction gratings and for measuring the width of a line constituting a diffraction grating
US5625453A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 26, 1994 |
| Grant date | Apr 29, 1997 |
| Priority date | — |
| Expiry date | Oct 26, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/70
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A deviation detecting system for detecting a relative positional deviation between first and second diffraction gratings, includes a light source, an illuminating device for projecting first and second light beams from the light source, having different directions of polarization, onto the first and second diffraction gratings along different directions, a first signal detecting device for detecting a first interference light signal from the first diffraction grating, being based on a combination of diffraction light of the first light beam and diffraction light of the second light beam, a second signal detecting device for detecting a second interference light signal from the second diffraction grating, being based on a combination of diffraction light of the first light beam and diffraction light of the second light, a first phase difference detecting device for detecting a phase difference between the first and second interference light signals and, a second phase difference detecting device for producing third and fourth interference light signals for correction of a phase error involved in the detected phase difference, and for detecting a phase difference between the third an…
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