Spectral filter
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United States of America Patent
Stats
-
Sep 19, 2017
Issued Date -
N/A
app pub date -
Jul 6, 1988
filing date -
Jul 10, 1987
priority date (Note) -
In Force
status (Latency Note)
Importance
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 may be periodic picket-fence reticles or different spatial frequencies may be used for the first and third reticles so as to vary the stop-band characteristics of the filter.
First Claim
Other Claims data not available
Family
International Classification(s)
- 1988 Application Filing Year
- G01J Class
- 310 Applications Filed
- 10 Patents Issued To-Date
- 3.23 % Issued To-Date
Cited Art Landscape
Patent Citation Ranking
- 0 Citation Count
- G01J Class
- 0 % this patent is cited more than
- 8 Age
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