Projection optical apparatus
US4883345A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 28, 1988 |
| Grant date | Nov 28, 1989 |
| Priority date | — |
| Expiry date | Dec 28, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70883
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An apparatus for projecting a pattern on a first plane onto a second plane comprises a projection lens system disposed between the first plane and the second plane and including a plurality of lens elements disposed at intervals, a plurality of spaces defined by the plurality of lens elements being formed, and means for isolating at least one of the plurality of spaces from the atmosphere. The at least one space is determined so that the variation in magnification of the projection lens system when the pressure in the at least one space varies with the atmospheric pressure is substantially equal to the variation in magnification of the projection lens system when all of the pressure in the space formed between the first plane and the projection lens system, the pressures in the plurality of spaces of the projection lens system and the pressure in the space formed between the projection lens system and the second plane vary with the atmospheric pressure.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.