Projection optical system
US4757354A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 28, 1987 |
| Grant date | Jul 12, 1988 |
| Priority date | — |
| Expiry date | Apr 28, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70225
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A projection optical system for photolithography includes a refraction sub-system and a cata-dioptric sub-system optically connected to each other. The refraction sub-system extends at an object side. The cata-dioptric sub-system extends at an image side. The refraction sub-system is generally composed of refracting members. The cata-dioptric sub-system is generally composed of a phase compensating member, a concave mirror, and a convex mirror. The phase compensating member adjoins the refraction sub-system. At least the concave mirror has a central opening through which light passes. The light forms an image at a rear of the concave mirror.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.