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Fiber optic sensor for detecting very small displacements of a surface

  • US 4,572,949 A
  • Filed: 12/14/1983
  • Issued: 02/25/1986
  • Est. Priority Date: 04/14/1982
  • Status: Expired due to Term
First Claim
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1. An apparatus for detecting small displacements of a surface comprising:

  • a first directional coupler for dividing a single coherent light signal into first and second coherent light signals;

    a first delay line for delaying said first coherent signal relative to said second coherent light signal by a first delay period to provide a delayed first light signal;

    a waveguide for directing each of said delayed first and said second light signals onto said surface to produce a first reflected light signal corresponding to said delayed first light signal and a second reflected light signal corresponding to said second light signal;

    a second delay line for delaying said second reflected light signal by said first delay period to produce a second delayed reflected light signal; and

    a detector for measuring the phase difference between said first reflected light signal and said second delayed reflected light signal to measure variations in the geometric path length between said waveguide and said surface.

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