Phase grating focus monitor using overlay technique
US6710853B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 31, 2001 |
| Grant date | Mar 23, 2004 |
| Priority date | — |
| Expiry date | May 4, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70641
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An optical tool includes a tool body that is transparent to light. Pluralities of parallel opaque lines on the body form a first outline in the shape of the square, and a second outline in the shape of a square which is centrally located relative to and within the first-mentioned square. Each pair of adjacent parallel lines has therebetween a first region that allows transmission of light therethrough without changing phase thereof, and a second region alongside the first region that allows transmission of light therethrough while shifting the phase thereof by 90°. The phase shifting and non-phase shifting regions are positioned so that the images of the outlines provided by a lens on an object shit in position a substantial amount as the distance between the lens and the object is changed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.