Projection optical system
US6275343A · kind A · utility
18Cited by
4References
8Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Apr 17, 2000 |
| Grant date | Aug 14, 2001 |
| Priority date | — |
| Expiry date | Apr 17, 2020 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B13/04
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A projection optical system has, from the enlargement side to the reduction side, a first, a second, and a third lens unit, and an aperture diaphragm. The negatively-powered first lens unit includes only a negative lens element and has at least one aspherical surface. The positively-powered second lens unit includes at least one positive lens element. The positively-powered third lens unit includes a lens element. The aperture diaphragm is disposed at the front focal point of the third lens unit. The lens element of the third lens unit is made of a material of which anomalous partial dispersibility and Abbe number are defined.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.