Apparatus and method of image enhancement through spatial filtering
US6525806B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Jun 29, 2000 |
| Grant date | Feb 25, 2003 |
| Priority date | — |
| Expiry date | Jun 29, 2020 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70308
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An image enhancement apparatus and method are disclosed. The apparatus consists of a spatial frequency filter where zero order mask diffraction information is reduced in an alternative pupil plane of the objective lens, specifically just beyond the mask plane. By introducing an angular specific transmission filter into this Fraunhofer diffraction field of the mask, user accessibility is introduced, allowing for a practical approach to frequency filtering. This frequency filtering is accomplished using a specifically designed interference filter coated over a transparent substrate. Alternatively, filtering can also be accomplished in a complimentary region near the wafer image plane or in both near-mask and near-wafer planes.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.