Position detection apparatus
US4710026A · kind A · utility
89Cited by
1References
17Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Mar 18, 1986 |
| Grant date | Dec 1, 1987 |
| Priority date | — |
| Expiry date | Mar 18, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7049
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An apparatus includes a means for providing a predetermined frequency difference between two light beams and generating an optical beat with respect to interference between first and second diffracted light beams from a diffraction grating formed on a substrate, and a means for detecting a phase difference between the optical beat and a reference signal having a frequency corresponding to the frequency difference between the two light beams, and detects a position of the substrate based upon the phase difference in accordance with an optical heterodyne interference method.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.