Photon intrusion detector
First Claim
Patent Images
1. An intrusion detector comprising:
- a light source having a certain correlation length;
first and second light paths, at least the first path extending through a secured area;
a modulator disposed in said second light path, wherein said modulator is selected from phase rotation and path length modulators;
at least one optical detector positioned to detect light from said first and second light paths and operable to generate a first signal in response thereto; and
a comparator electrically coupled to said optical detector to compare said first signal with a second signal applied to said modulator.
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Abstract
An intrusion detector and method of operation which include a light source having a certain correlation length, and first and second light paths, wherein at least the first path extends through a secured area. A modulator, which is advantageously either a phase rotation modulator or path length modulator, is provided in the second path. At least one optical detector is placed to detect light traveling along the two paths. A comparator is electrically coupled to the detector to compare the detected signal with a signal applied to the modulator.
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Citations
17 Claims
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1. An intrusion detector comprising:
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a light source having a certain correlation length;
first and second light paths, at least the first path extending through a secured area;
a modulator disposed in said second light path, wherein said modulator is selected from phase rotation and path length modulators;
at least one optical detector positioned to detect light from said first and second light paths and operable to generate a first signal in response thereto; and
a comparator electrically coupled to said optical detector to compare said first signal with a second signal applied to said modulator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for detecting an intruder comprising:
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splitting a light beam having a known correlation length into a first beam traveling along a first optical path and a second beam traveling along a second optical path, wherein at least said first optical path extends through a secured area;
modulating said second beam with a first signal;
combining said first beam and said second beam;
detecting light from the combined beams and generating a second signal in response thereto; and
comparing said second signal with said first signal. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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Specification