Spectral filter
US9766128B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 6, 1988 |
| Grant date | Sep 19, 2017 |
| Priority date | — |
| Expiry date | Jul 6, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01J2003/1278
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A filter for removing coherent radiation from a source in a field of view, substantially independent of the size of the source, comprises a first reticle 22 located in the path of received light 21, a first lens 23 producing an optical transform of the first reticle 22 at a second reticle 24 located in the image plane of the first lens 23, a second lens 25 producing an optical transform of the second reticle 24 and a third reticle 26 located in the image plane of the second lens 25. The arrangement is such that the spatial transmittance of the third reticle 26 is selected to block at least part of the diffracted image of the first reticle 22 produced in the image plane of the second lens 25 and characteristic of the coherent radiation. Preferably the optical transforms are Fourier Transforms. A monochromatic coherent source in the field of view produces a pattern of diffracted energy in the image plane of the second lens which is independent of the size of the source. Thus, by providing a suitable reticle 26 in the image plane of the second lens light from a coherent source in the field of view can be blocked while polychromatic light is transmitted. The first and second reticles m…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.