Fiber optic bending and positioning sensor with selected curved light emission surfaces

• US 5,633,494 A
• Filed: 09/22/1995
• Issued: 05/27/1997
• Est. Priority Date: 07/31/1991
• Status: Expired due to Term

• Current Assignee: 059312 N.B. Inc., Bank of Montreal
• Original Assignee: Lee Danisch
• Inventors: Danisch, Lee
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US08/532,327
• Time in Patent Office: 613 Days
• Field of Search: 250/227.16, 250/227.14, 250/227.24, 250/227.31, 385/32, 385/39, 385/48, 385/13
• US Class Current: 250/227.16
• CPC Class Codes: G01D 5/35377 Means for amplifying or modifying the measured quantity
• CPC Class Codes: G02B 6/02057 comprising gratings
• CPC Class Codes: G02B 6/2852 using tapping light guides arranged sidewardly, e.g. in a non-parallel relationship with respect to the bus light guides (light extraction or launching through cladding, with or without surface discontinuities, bent structures)

Abstract

A curvature or bending and displacement sensor is composed of a fiber optic or light wave guide, for attachment to a member or members being curved or displaced. Light is injected at one end and detected at the other end. Curvature of the fiber results in light loss through an emission surface or surfaces, sometimes in conjunction with a superimposed curvature in a plane other than that of the curvature to be measured, this loss being detected. The loss of light detection is used to produce indication of curvature or displacement. The light emission surfaces extend in various forms, such as a surface strip or band. Particularly, in an example, the emission surfaces extend in a substantially peripheral direction, or in a substantially curved axial direction when in a curved portion of a curved guide. The placement, shape and configuration of the emission surfaces allows adjustment of the linear range of measurement, the overall throughput of light, and the length over which curvature is measured. Two or more light guides can be oriented to given indication of direction of curvature or displacement.

Claims

1. A fiber optic bending and position sensor comprising a fiber optic light guide having a peripheral surface and having at least one curved light emission surface extending for part of the length of said light guide, said at least one curved light emission surface extending at said peripheral surface in a direction selected from (a) extending around said peripheral surface, (b) extending in an axial direction along said peripheral surface at a curved portion of said light guide and including means for injecting a light beam into an end of said light guide and means for detecting said light beam after it has passed the light emission surface zone.

2. A sensor as claimed in claim 1, wherein the light emission surface or surfaces are positioned to give a maximum change in light intensity transmitted through the fiber optic light guide when said sensor is bent in a selected plane.

3. A sensor as claimed in claim 1 including means for measuring the difference in intensity of said light beam between said one end and said other end of said light guide.

4. A sensor as claimed in claim 3 including display means for indicating any said difference in intensity of said light beam as a bending or displacement of said light guide.

5. A sensor as claimed in claim 1 including a further fiber optic light guide positioned alongside said fiber optic light guide, said further light guide having an unbroken cladding layer and forming a reference light guide.

6. A sensor as claimed in claim 1 having said at least one curved light emission surface covered by a light absorbent material.

7. A sensor as claimed in claim 1 comprising a fiber optic light guide in the form of a loop, the loop having said curved light emission surface therein.

8. A sensor as claimed in claim 7, wherein the loop has a plurality of curved light emission surface regions therein.

9. A sensor as claimed in claim 8, wherein said curved light emission surface regions in the curved loop comprise peripherally-oriented bands grouped on an inside or concave portion of the curvature of the loop.

10. A sensor as claimed in claim 9 having three to five peripherally-oriented bands grouped together, with the bands each extending for about 60°

to about 90°

.

11. A sensor as claimed in claim 8, wherein said curved light emission surface regions in the curved loop comprise axially-oriented bands with their axial edges substantially in a plane parallel to the planes described by the uppermost and lowermost reaches of said loop and following the curvature of the loop.

12. A sensor as claimed in claim 11 having from two to six curved bands in parallel planes.

13. A sensor as claimed in claim 7, wherein said light emission surface is positioned to gain a maximum change in light intensity transmitted through the fiber optic light guide when said sensor is bent in a selected plane.

14. A sensor according to claim 1, wherein the sensor is a suspension sensor comprising a flexible beam, said fiber optic bending and position sensor mounted on said flexible beam.

15. The sensor of claim 1 in which at least a portion of said fiber optic light guide is in the form of a single fiber which serves both to illuminate said at least one light emission surface and to collect illumination which has passed said at least one light emission surface, the illumination and collection end or ends of the fiber being located in a single region remote from the light emission surface or surfaces.

16. The sensor of claim 15, wherein the single fiber forms a loop, at least a portion of the light emission surface is in the loop, and the apex of the loop is at the distal extremity remote from said single region.

17. A fiber optic bending and position sensor comprising a fiber optic light guide having at least one curved light emission surface extending for part of the length of said light guide, said at least one curved light emission surface comprising at least one band extending peripherally of said light guide including means for injecting a light beam into an end of said light guide and means for detecting said light beam at the other end of said light guide.

18. A sensor as claimed in claim 17 having the light emission surface in the form of a plurality of spaced apart peripherally-oriented bands covered with a light-absorbing material.

19. A fiber optic bending and position sensor comprising a fiber optic light guide having at least one curved light emission surface extending for part of the length of said light guide, said curved light emission surface comprising at least one band extending axially at a curved portion of said light guide including means for injecting a light beam into an end of said light guide and means for detecting said light beam at the other end of said light guide.

20. A sensor as claimed in claim 19 wherein said fiber optic light guide has a rectangular cross-section, with said at least one curved light emission surface being on at least one side of said cross-section at a curved portion of said light guide and each said emission surface being covered with a light-absorbing material.

21. A sensor as claimed in claim 20, said rectangular cross-section being oblong and including two spaced parallel wide sides, said at least one curved light emission surface on one of said wide sides.

22. A sensor as claimed in claim 21, wherein said light guide is bent into a U-shape on a plane parallel to planes of said wide sides, said bend forming said curved portion.

23. A sensor as claimed in claim 21, said light guide being bent into a U-shape in a plane normal to said planes of said wide sides, said bend forming said curved portion.

24. A sensor as claimed in claim 23 with a light emission surface on each of said wide sides, at said bend.

25. A sensor as claimed in claim 19 wherein said fiber optic light guide has a D-shaped cross-section, having a flat surface on one side, said light emission surface being formed on said flat surface.

26. A method of sensing curvature and displacement of an elongate member, comprising:

attaching a fiber optic light guide to said elongate member, said light guide having a peripheral surface and having a curved light emission surface on said peripheral surface and extending for part of the length of said light guide, said curved light emission surface extending in a direction selected from (a) extending peripherally around said peripheral surface, (b) extending axially along said peripheral surface at a curved portion of said light guide;

injecting a light beam into one end of said light guide;

detecting said light beam at the other end of said light guide;

measuring the difference in intensity of said light beam between said one end and said other end; and

indicating bending, or displacement, of said elongate member.

27. The method of claim 26 including attaching a plurality of fiber optic light guides to said elongate member, each light guide having a plurality of light emission surfaces, said light emission surfaces on each individual light guide being positioned to give a maximum change in light intensity transmitted through said individual light guide when said elongate member is bent in a unique selected plane.

28. The method as claimed in claim 27 utilizing two to six fiber optic light guides, said surfaces oriented in different directions at predetermined angles relative to each other.

29. The method as claimed in claim 26 including attaching a further fiber optic light guide alongside said fiber optic light guide, said further fiber optic light guide acting as a reference light guide.

30. The method of claim 26 which includes selecting the size, shape and orientation of each of the emission surfaces of the light guide so as to optimize sensing of curvatures, including curvature changes that produce increasing transmission of light with increasing curvature.

31. The method of claim 26 which includes the use of shear elements or springs between at least one end portion of said elongate member and a moveable member, the displacement of which it is desired to be measured, to communicate displacement to the elongate member, such that curvature of said elongate member maximally represents the moveable member displacement to be measured.

32. A fiber optic bending and position sensor comprising, a fiber optic light guide in the form of a loop having a tight curve portion, with at least one curved light emission surface substantially on said tight curve portion, the size and positioning of the light emission surface being selected to increase sensitivity to deformation, means for injecting a light beam into one end of said light guide and means for detecting the light beam after it has passed the light emission surface zone.

33. The sensor of claim 32 wherein the light emission surface covers only part of the circumference, is axially-extending and covered by a light-absorbing material, the tight curve portion forms a semi-circular shape, and a deformation to be sensed tends to deform or deflect the semi-circular shaped portion.