Fiber optic displacement measuring apparatus

• US 3,940,608 A
• Filed: 02/04/1974
• Issued: 02/24/1976
• Est. Priority Date: 02/04/1974
• Status: Expired due to Term

• Current Assignee: Mechanical Technology Incorporated
• Original Assignee: Mechanical Technology Incorporated
• Inventors: Kissinger, Curtis D., Howland, Bradford
• Primary Examiner(s): Rubin, David H.
• Application Number:
  US05/439,339
• Time in Patent Office: 750 Days
• Field of Search: 350/96 B, 350/214, 350/222, 350/175 TS, 250/227, 356/125, 356/156, 356/4
• US Class Current: 250/227.28
• CPC Class Codes: G01D 5/268 using optical fibres G01D5/28 - G01D5/38 take precedence

Abstract

Fiber optic displacement/position measuring apparatus having increased working distance and measuring range capability is provided by combining an optical extending sensing head in fixed relationship with the common end of a bifurcated fiber optic bundle. The sensing head includes a lens system which is operative to focus the image of the end face of the fiber optic bundle onto the surface of an object whose displacement is to be determined and to refocus that image back onto the end in an upright relationship.

Claims

1. Optical apparatus for determining the displacement or position of an object comprising:

a. A light source and a light receiver for receiving light transmitted from said light source;

b. A fiber optic conduit of Y-shaped configuration having the end of one arm thereof positioned adjacent said light source and the other arm positioned adjacent said light receiver, said conduit arms forming a common bundle of optically conducting fibers in the base of said Y, some of which fibers are transmitting fibers for conducting light from said light source to a surface of said object and some of which are receiving fibers for conducting light reflected from the surface of said object to said light receiver so that said conduit is normally operative to conduct light from said light source and to conduct reflected light impinging on the end face of said common bundle to said light receiver; and

c. A sensing head having one end thereof fixedly mounted with the end of said common bundle and the other end adapted to be positioned adjacent the surface whose displacement or position is to be measured, said sensing head including lens means comprising a pair of projection lenses arranged in back-to-back relationship and operative to focus the image of the end face of said common bundle onto the surface of said object and refocus said image back onto said end face to provide for a minimum output from said light receiver for a given distance between said end of said sensing head and the surface of said object and an increase in output from said light receiver for any change in said given distance.

2. The optical apparatus recited in claim 1 wherein the optically conducting transmitting and receiving fibers of the common bundle are randomly dispersed.

3. The optical apparatus recited in claim 1 wherein said lens means includes means for changing the magnification ratio.

4. The optical apparatus recited in claim 3 wherein each of said lenses is a microscope type lens.

5. The optical apparatus recited in claim 3 wherein said means for changing the magnification ratio of said lens means comprises substitution of one of the lenses of said pair.

6. The optical apparatus recited in claim 1 wherein said sensing head includes means for adjusting the distance between the end face of the common bundle and the lens means.

7. The optical apparatus recited in claim 1 wherein said lens means includes means for varying the aperture thereof.

9. The optical apparatus recited in claim 1 wherein said lens means is operative to focus the image of the end face of said common bundle onto the surface of said object in a 1:

1 relationship.

10. The optical apparatus recited in claim 1 wherein said lens means is operative to focus the image of the end face of said common bundle onto the surface of said object in greater than a 1:

1 relationship.

11. The optical apparatus recited in claim 1 wherein said lens means is operative to focus the image of the end face of the common bundle onto the surface of said object in less than a 1:

1 relationship.

8. In an optical apparatus for determining the displacement or position of an object having a fiber optic proximitor of the type comprising a fiber optic conduit of Y-shaped configuration having the end of one arm thereof positioned adjacent a light source, the end of the other arm positioned adjacent a light receiver and wherein the arms form a common bundle of optically conducting fibers in the base of the Y terminating in an end face which includes the ends of transmitting fibers for conducting light from said light source to a surface of said object and the ends of receiving fibers for conducting light reflected from the surface of said object to said light receiver so that light transmitted from the light source and reflected from the surface of an object normally impinges on said end face so as to be received by said light receiver and provide for an output therefrom;

the improvement which comprises;

a. An optical extending sensing head having one end thereof mounted to the end of said common bundle and the other end adapted to be positioned adjacent the surface of an object whose displacement is to be determined, said sensing head including lens means comprising a pair of projection lenses arranged in back-to-back relationship and operative to focus the image of the end face of said common bundle onto the surface of said object and refocus said image back onto said end face to provide for a minimum output from said light receiver for a given distance between said end of said sensing head and the surface of said object and an increase in output from said light receiver for any change in said given distance.