Coherent laser warning system
AssigneeThe Boeing Company
InventorJames C. Russell
Life of this patent
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Abstract
An interferometer, preferably a wedge etalon, produces a spatial pattern of fringes when incident radiant energy is coherent. A system for analyzing these fringes uses a transform operation to detect spatial regularity. The transform operation may be electronic (computational) based on the output of individual photodetectors of an array disposed adjacent to the interferometer, or optical by a Fourier transform lens disposed adjacent to the interferometer. In either case, the combination of fringe creating element and transform operation permits the unambiguous detection of light with a coherence length longer than that of natural light, such as from a laser.
Claims13
A system for detecting coherent radiant energy having a frequency of interest comprising:
- an interferometer for producing a pattern of regularly spaced intensity fringes when impinged on by coherent radiant energy having a frequency of interest, the regular pattern including several intensity fringes with adjacent fringes spaced apart by a uniform distance, the interferometer being an etalon having top and bottom partially reflective surfaces spaced apart by a transmissive material, said top and bottom surfaces being spaced apart by a continuously variable distance along one dimension of the etalon, at least one of the top and bottom etalon surfaces being arcuate;
- and
- a transform element for analyzing a pattern of fringes produced by the interfering element to detect the pattern by performance of a spatial Fourier transform operation.
A system for detecting coherent radiant energy having a frequency of interest comprising:
- an etalon having top and bottom partially reflective surfaces spaced apart by a transmissive material, said top and bottom surfaces being spaced apart by a continuously variable distance along one dimension of the etalon for producing a spatial array of intensity fringes when impinged on by coherent radiant energy having a frequency of interest, at least one of the top and bottom etalon surfaces being arcuate;
- and
- a transform element for analyzing a spatial array of fringes produced by the etalon to detect the array by performance of a spatial Fourier transform operation.
Dependencies are inferred from the claim text.