Structural analyzer using acousto-optic sensor

• US 5,600,133 A
• Filed: 05/01/1995
• Issued: 02/04/1997
• Est. Priority Date: 03/22/1993
• Status: Expired due to Term

• Current Assignee: Simmonds Precision Products, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Simmonds Precision Products, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Spillman, William B. Jr.
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): Lee, John R.
• Application Number:
  US08/431,484
• Time in Patent Office: 645 Days
• Field of Search: 250/227.14, 250/227.16, 250/227.21, 385/12, 385/13, 367/140, 73/624, 73/655, 73/600, 73/644, 73/627, 73/606, 73/607, 73/603, 73/598, 73/632, 73/656, 73/657, 73/696, 73/643, 73/645, 73/646
• US Class Current: 250/227.14
• CPC Class Codes: G01N 29/2418 using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics photoacoustic cells G01N21/1702; measuring characteristics of vibrations by using radiation-sensitive means G01H9/00; acousto-optical conversion techniques for short-range imaging G01S15/8965; sound-producing devices using laser bundle G10K15/046

Abstract

An acousto-optic damage detector and locator uses acoustic energy propagated through a structure to modulate light transmitted through an optical fiber whereby the character of acoustic signals detected by the fiber varies according to the physical condition of the portion of the structure through which the pulses propagate to determine the existence, location and extent of faults within the structure.

Claims

1. An acousto-optic structure analyzer comprising,

means for transmitting acoustic energy through an elongated acoustic wave guide that is acoustically coupled along its length to the structure so that acoustic energy is transmitted through at least a corresponding portion of the structure along the length of said wave guide to produce a transmissive acoustic signature distributed over said length, and

means for modulating light in response to said acoustic energy to produce a light pattern representative of said distributed acoustic signature.

2. The analyzer of claim 1 wherein said wave guide is embedded within said structure.

3. The analyzer of claim 1 wherein said means for modulating light in response to said acoustic signature comprises an optical fiber.

4. The analyzer of claim 3 wherein said optical fiber is physically coupled to said structure.

5. The analyzer of claim 3 wherein a portion of said optical fiber is within said structure.

6. The analyzer of claim 1 further comprising means for detecting light modulated in response to said acoustic signature.

7. The analyzer of claim 6 wherein said means for detecting light comprises means for detecting the intensity of said light.

8. The analyzer of claim 6 wherein said means for detecting light comprises an interferometer.

9. The analyzer of claim 6 wherein said means for detecting light comprises a diffraction grating.

10. The analyzer of claim 1 wherein said modulating light means comprises an optic fiber that coextends along the structure with said wave guide means to detect said transmitted acoustic energy distributed through the structure along the length of said wave guide.

11. The analyzer of claim 10 wherein acoustic energy is distributed through said corresponding structure portion along said wave guide length by leaking from said wave guide into the structure along said wave guide length acoustically attached to the structure.

12. The analyzer of claim 11 wherein said wave guide is embedded in the structure.

13. The analyzer of claim 11 wherein said optic fiber is embedded in the structure.

14. The analyzer of claim 1 further comprising an acoustic energy source that transmits acoustic energy into said wave guide, said acoustic energy propagating along said wave guide means for a determinable time period T such that acoustic energy distributively leaks into the structure towards said light modulating means along said length of the wave guide, so that modulated light signals detected during said period T represent an acoustic signature of the structure along a distributed portion of the structure.

15. The analyzer of claim 14 further comprising means for detecting said light pattern and producing first signals representative thereof during at least the time period T, and means for comparing said first signals with corresponding second signals representative of a reference pattern.

16. A method for analyzing a structure comprising the steps of,

providing an elongated acoustic wave guide acoustically coupled along its length to the structure;

transmitting acoustic energy along the length of the wave guide into a corresponding portion of the structure to be analyzed to produce a distributed transmissive acoustic signature, and

modulating light in response to said distributed acoustic signature to produce a light pattern that represents said signature.

17. The method of claim 16 further including the step of detecting said light modulated in response to said acoustic signature.