| 摘要 |
A motion detector for detecting motion of a body in a surveillance zone comprising: at least one laser that produces laser light; at least one photodetector that generates signals responsive to light incident thereon; a light distributor that receives laser light from a laser of the at least one laser and distributes a portion of the light into a plurality of sensor light beams that extend into the surveillance zone and a portion of the light into at least one reference light beam, which does not extend into the surveillance zone, said at least one reference beam being incident on a region of the at least one photodetector, wherein the distributor is positioned and configured so that light reflected from a sensor beam by an object in the surveillance zone is received by the distributor and directed onto said region of the at least one photodetector; and circuitry that receives signals generated by the at least one photodetector and processes the signals to determine if reflected light incident on the at least one detector is Doppler shifted as a result of motion of the body, and if so, generates a signal indicating motion of the body.
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