On-axis interferometric alignment of plates using the spatial phase of interference patterns
US5414514A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 1, 1993 |
| Grant date | May 9, 1995 |
| Priority date | — |
| Expiry date | Jun 1, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J37/3045
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
There are first and second relatively movable plates. On a face of each of the first and second plates, there are first and second alignment marks, each being a linear grating of parallel lines of uniform spatial period, the spatial periods being different from each other. There is a light source for illuminating the linear grating on the second plate through the linear grating on the first plate to produce an interference pattern. Indicia on the first or second plates indicate a periodic reference pattern having a phase. A detector is configured to detect when the spatial phase of the interference pattern and the spatial phase of said reference pattern differ by a predetermined value. A position adjustor is for adjusting the relative position of the first and second plates until the detector detects said phase difference.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.