The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 19, 2017
Filed:
Jul. 06, 1988
Herbert A. French, Emsworth, GB;
Philip Sutton, Chandler's Ford, GB;
Herbert A. French, Emsworth, GB;
Philip Sutton, Chandler's Ford, GB;
QINETIQ LIMITED, Farnborough, GB;
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 reticlelocated in the path of received light, a first lensproducing an optical transform of the first reticleat a second reticlelocated in the image plane of the first lens, a second lensproducing an optical transform of the second reticleand a third reticlelocated in the image plane of the second lens. The arrangement is such that the spatial transmittance of the third reticleis selected to block at least part of the diffracted image of the first reticleproduced in the image plane of the second lensand 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 reticlein 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.