Focusing apparatus for projection optical system
US4650983A · kind A · utility
152Cited by
2References
18Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Nov 2, 1984 |
| Grant date | Mar 17, 1987 |
| Priority date | — |
| Expiry date | Nov 2, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7026
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A focusing apparatus for projection optical system is provided with a projection optical system and an image-forming optical system. The projection optical system is disposed to project an image of an alignment mark formed on a photo mask or reticle onto a light-reflective substrate and also to reverse-project onto the photo mask the light image of the alignment mark projected on and reflected by the substrate. The image-forming optical system forms an overlap image from the reverse-projected reflected image and the alignment mark on the photo mask.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.