Optical deformation sensor

• US 4,420,251 A
• Filed: 12/28/1981
• Issued: 12/13/1983
• Est. Priority Date: 05/05/1980
• Status: Expired due to Term

• Current Assignee: Rockwell International Corporation
• Original Assignee: Rockwell International Corporation
• Inventors: James, Kenneth A., Strahan, Virgil H., Quick, William H., August, Rudolf R.
• Primary Examiner(s): Punter, William H.
• Application Number:
  US06/334,998
• Time in Patent Office: 715 Days
• Field of Search: 356/32-35, 356/35.5, 356/351, 356/73.1, 250/225, 250/227, 350/96.1, 350/385, 350/96.15, 350/96.16, 73/655-657, 73/704, 73/800
• US Class Current: 356/32
• CPC Class Codes: G01B 11/16 for measuring the deformation in a solid, e.g. optical strain gauge
• CPC Class Codes: G01L 1/243 using means for applying force perpendicular to the fibre axis
• CPC Class Codes: G01M 11/083 by using an optical fiber in contact with the device under test [DUT]

Abstract

This invention relates to a lightweight and compact optical sensor that provides an indication of a deformation (e.g. fatigue, vibration, flex, torsion, bending, slippage) occurring at a monitored area. The sensor includes at least one light transmitting optical fiber and an optical detector that is responsive to the optical characteristics (e.g. amplitude, phase, polarization angle) of a supply of light signals being transmitted through the fiber. In the event that deformation occurs at the monitored region, the optical fiber undergoes a displacement which thereby causes a corresponding change in the optical characteristics of the light signals supplied to the detector. The optical characteristics of the light signals supplied to the detector relative to those of the light signals supplied to the optical fiber provide an accurate indication of the physical parameter.

Claims

1. An optical sensor to provide an indication of a physical parameter, said optical sensor comprising:

source means for providing a supply of incident light signals,

first optical means to polarize said incident light signals,

second optical means arranged so as to selectively transmit polarized light signals that are supplied thereto,

at least one light transmitting optical fiber aligned at a first end thereof with each of said first and second optical means for receiving polarized incident light signals from said first optical means,

light reflecting means aligned with the second end of said optical fiber to thereby reflect polarized light signals that are transmitted thereto via said optical fiber back through said optical fiber and to said second optical means, and

optical detector means aligned to receive polarized output light signals that are selectively transmitted from said optical fiber through said second optical means, said detector means being responsive to the optical characteristics of the output light signals,

said optical fiber undergoing a corresponding deformation in response to a physical parameter, whereby to alter the optical characteristics of the light signals being transmitted therethrough,

the optical characteristics of the output light signals that are transmitted to said optical detector means through said second optical means relative to the optical characteristics of the incident light signals supplied to said optical fiber from said first optical means providing an indication of the physical parameter.

2. The optical sensor recited in claim 1, wherein the first end of said optical fiber comprises a relatively enlarged terminal to increase the optical coupling of light signals into and out of said fiber,

said enlarged terminal having at least one flat face, and

at least one of said first and second optical means positioned on the flat face of said terminal.

3. The optical sensor recited in claim 2, wherein the second end of said optical fiber comprises a relatively enlarged terminal having at least one flat face,

said light reflecting means positioned on the flat face of said last-mentioned terminal.

4. The optical sensor recited in claim 1, wherein said first and second optical means include respective grating patterns that are rotated out of alignment relative to one another.

5. The optical sensor recited in claim 4, wherein one of said first or second optical grating patterns is rotated with respect to the other, so that said grating patterns are 90 degrees out of alignment with one another.

6. The optical sensor recited in claim 1, wherein each of said first and second optical means comprises a diffraction grating.