Fiber optic sensor for precision 3-D position measurement
First Claim
1. Apparatus comprising an optical medium having curved sections, said medium including a plurality of single mode cores, said cores being closely spaced to exhibit cross-talk therebetween, said cross-talk exhibiting changed values only at bends in said medium, said apparatus including a broadband source for illuminating said cores sequentially, means for measuring the spectral intensities including the magnitude of light signals at different freguencies of the entire plurality of cores each time a core is illuminated, and means responsive to said spectral intensities for determining the positions of said curved sections.
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Abstract
The central system component of the present invention is a flexible “smart cable” which enables accurate measurement of local curvature and torsion along its length. These quantities are then used to infer the position and attitude of one end of the cable relative to the other. Sufficiently accurate measurements of the local curvature and torsion along the cable allow reconstruction of the entire cable shape, including the relative position and orientation of the end points. The smart cable for making these measurements comprises a multicore optical fiber, with individual fiber cores constructed to operate in the single mode regime, but positioned close enough to cause cross-talk (mode coupling) between cores over the length of the fiber. This cross-talk is very sensitive to the distribution of strains (curvature and torsion) along the cable.
362 Citations
13 Claims
- 1. Apparatus comprising an optical medium having curved sections, said medium including a plurality of single mode cores, said cores being closely spaced to exhibit cross-talk therebetween, said cross-talk exhibiting changed values only at bends in said medium, said apparatus including a broadband source for illuminating said cores sequentially, means for measuring the spectral intensities including the magnitude of light signals at different freguencies of the entire plurality of cores each time a core is illuminated, and means responsive to said spectral intensities for determining the positions of said curved sections.
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5. A positioning sensor comprising an optical fiber cable having multiple, closely positioned single mode cores;
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a broadband illumination source for sequentially illuminating said cores;
a spectral intensity measurement device for measuring the spectral characteristics including the magnitude of light signals at different freguencies of all of said cores after each said core is illuminated by said source; and
an inversion calculation apparatus for determining local curvature and torsion along said fiber cable and calculating cable end-point position and orientation from said spectral intensity measurements. - View Dependent Claims (6, 7, 8, 9)
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10. A method for measurement of the position of one end of a fiber optic cable relative to a known position of another end of the fiber optic cable, the cable having a plurality of closely-positioned single-mode cores;
- the method comprising the steps of;
a) illuminating each of said cores with a source of boradband energy;
b) measuring the spectral intensities including the magnitude of light signals at different frequencies of all of said cores as each said core is illuminated;
c) determining the curvature and torsion characteristics of said cable based upon said spectral intensities; and
d) inferring the position of said one end from said curvature and torsion characteristics. - View Dependent Claims (11, 12, 13)
- the method comprising the steps of;
Specification