Optical filter for incoherent imaging systems
US4804249A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 24, 1986 |
| Grant date | Feb 14, 1989 |
| Priority date | — |
| Expiry date | Dec 24, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B27/0025
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An optical filter for use with an imaging lens in an incoherent imaging system operating in broadband illumination for increasing the depth-of-focus of the lens while maintaining energy thru-put is disclosed. The optical filter comprises a transparent support having on one surface thereof an array of transparent, discrete steps of substantially equal size, each step having a thickness that differs from all other steps by at least the coherence length of the radiation to be passed and the size of the array being equal to the size of the lens. In use, the optical filter is positioned in front of the imaging lens. When so positioned, the depth of focus of the imaging lens is proportional to the size of the individual steps rather than the size of the lens while the energy thru-put of the imaging remains the same as it would be without the optical filter.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.