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US 4,397,548 AGranted
Distance measuring system
AssigneeThe United States of America as represented by the Secretary of the Army
InventorRay G. McCormack
Life of this patent
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Abstract
A modulated light beam from a radiation source on a structure whose posit is to be measured is split into a first beam which propagates through the atmosphere to a first detector and a second beam which travels through an optical fiber to a second detector. The first and second detectors recover the modulation on the first and second beams, the phases of which are compared to determine the distance. In a preferred embodiment, the light source is a sine-wave modulated laser.
Claims3
Apparatus for measuring a variable distance between a first point and a second point comprising:
- means at said first point for providing a modulated beam of light;
- means for directly transmitting said first modulated beam of light said distance to said second point;
- an optical fiber having a substantially fixed optical path length;
- said optical fiber being effective to transmit said second modulated beam over said substantially fixed optical path length from said means for splitting to said second point;
- said optical fiber being disposed adjacent said first beam of light the full distance between said first and second points;
- means at said second point for separately recovering modulation from said first and second modulated beams to produce first and second modulation signals respectively;
- and
- means for comparing a phase of said first and second modulation signals to determine said variable distance.
5 more elements
Dependencies are inferred from the claim text.