Dual-interferometer method for measuring bending of materials
First Claim
1. A method of using two interferometric configurations to measure bending of an extended structural element, comprising the steps of:
- attaching a segment of a first optical fiber along one side of the element, the first optical fiber comprising the measurement arm of a first interferometric configuration, the first interferometric configuration having a reference arm and selected from the group consisting of a Michelson or Mach-Zehnder interferometer;
obtaining a set of interference fringe values from the first interferometric configuration;
attaching a segment of a second optical fiber along one side of the element and another segment of the second optical fiber along the opposing side of the element, the second optical fiber comprising the measurement arm of a second interferometric configuration, the second interferometric configuration having a reference arm and selected from the group consisting of a Michelson or Mach-Zehnder interferometer;
obtaining a set of interference fringe values from the second interferometer configuration;
subtracting the second set of interference fringe values from the first set of interference fringe values; and
calculating bending of the element based on the results of the subtracting step.
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Abstract
A method of two interferometric configurations to measure bending of an extended element. The measurement arm of each configuration is a long optical fiber. A first interferometric configuration has a segment of its measurement arm attached to one side of the element. The second interferometric configuration has a segment of its measurement arm attached to one side of the element and another segment of its measurement arm attached to an opposing side of the element. The two configurations are used to obtain two sets of interference fringe measurement values. If one set is subtracted from the other, the result is intensity differential values that indicate only the effects of bending and not of temperature or pressure. Variations of the method can be used for irregularly shaped elements.
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Citations
12 Claims
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1. A method of using two interferometric configurations to measure bending of an extended structural element, comprising the steps of:
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attaching a segment of a first optical fiber along one side of the element, the first optical fiber comprising the measurement arm of a first interferometric configuration, the first interferometric configuration having a reference arm and selected from the group consisting of a Michelson or Mach-Zehnder interferometer;
obtaining a set of interference fringe values from the first interferometric configuration;
attaching a segment of a second optical fiber along one side of the element and another segment of the second optical fiber along the opposing side of the element, the second optical fiber comprising the measurement arm of a second interferometric configuration, the second interferometric configuration having a reference arm and selected from the group consisting of a Michelson or Mach-Zehnder interferometer;
obtaining a set of interference fringe values from the second interferometer configuration;
subtracting the second set of interference fringe values from the first set of interference fringe values; and
calculating bending of the element based on the results of the subtracting step. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of using two interferometric configurations to measure bending of an extended structural element, comprising the steps of:
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determining a pair of surfaces of the element, along which the effects of bending are canceled;
attaching a segment of a first optical fiber along a first of the two surfaces, the first optical fiber comprising the measurement arm of a first interferometric configuration;
obtaining a set of interference fringe values from the first interferometric configuration;
attaching a segment of a second optical fiber along the first of the two surfaces and another segment of the second optical fiber along the second of the two surfaces, the second optical fiber comprising the measurement arm of a second interferometric configuration;
obtaining a set of interference fringe values from the second interferometer configuration;
subtracting the second set of interference fringe values from the first set of interference fringe values; and
calculating bending of the element based on the results of the subtracting step. - View Dependent Claims (9)
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10. A method of using two interferometric configurations to measure bending of an extended structural element, comprising the steps of:
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attaching a segment of a first optical fiber along one side of the element, the first optical fiber comprising the measurement arm of a first interferometric configuration;
obtaining a set of interference fringe values from the first interferometric configuration;
determining a surface of the element along which no length difference occurs due to bending of the element;
attaching a segment of a second optical fiber along the surface determined by the preceding step, the second optical fiber comprising the measurement arm of a second interferometric configuration;
obtaining a set of interference fringe values from the second interferometer configuration;
subtracting the second set of interference fringe values from the first set of interference fringe values; and
calculating bending of the element based on the results of the subtracting step. - View Dependent Claims (11)
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12. A method of using two interferometric configurations to measure bending of an extended structural element, comprising the steps of:
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attaching a segment of a first optical fiber along one side of the element, the first optical fiber comprising the measurement arm of a first interferometric configuration, the first interferometric configuration having a reference arm and selected from the group consisting of a Michelson or Mach-Zehnder interferometer;
obtaining a set of interference fringe values from the first interferometric configuration;
attaching a segment of a second optical fiber along one side of the element and another segment of the second optical fiber along the opposing side of the element, the second optical fiber comprising the measurement arm of a second interferometric configuration, the second interferometric configuration having a reference arm and selected from the group consisting of a Michelson or Mach-Zehnder interferometer;
obtaining a set of interference fringe values from the second interferometer configuration;
simultaneously solving equations representing the relationship among the interference fringe values and bending, temperature, and pressure; and
calculating bending of the element based on the results of the solving step.
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Specification