Systems and methods for automatic alignment and focusing of light in laser ultrasound testing

Patent metadata

Field	Value
Publication number	US-2020141908-A1
Application number	US-201816183229-A
Country	US
Kind code	A1
Filing date	Nov 7, 2018
Priority date	Nov 7, 2018
Publication date	May 7, 2020
Grant date	—

Abstract

A method for testing a structure using laser ultrasound includes steps of: (1) directing positioning light on a surface of the structure; (2) determining a spatial location and a spatial orientation of the surface from an evaluation of the positioning light reflected back from the surface; (3) directing pump light onto the surface to generate ultrasonic waves in the structure; (4) selectively locating a probe-light focal point of probe light on the surface, based on the spatial location determined for the surface; (5) selectively angularly orienting the probe light normal to the surface, based on the spatial orientation determined for the surface; and (6) directing the probe light onto the surface to detect a response to the ultrasonic waves.

First claim

What is claimed is:

1 . A method for testing a structure using laser ultrasound, the method comprising steps of:
directing positioning light on a surface of the structure; determining a spatial location and a spatial orientation of the surface from an evaluation of the positioning light reflected back from the surface; directing pump light onto the surface to generate ultrasonic waves in the structure; selectively locating a probe-light focal point of probe light on the surface, based on the spatial location determined for the surface; selectively angularly orienting the probe light normal to the surface, based on the spatial orientation determined for the surface; and directing the probe light onto the surface to detect a response to the ultrasonic waves.

2 . The method of claim 1 , further comprising:
evaluating the response to generate information about the structure; and determining whether an anomaly is present in the structure, based on the information generated about the structure.

3 . The method of claim 1 , wherein the step of selectively locating the probe-light focal point of the probe light on the surface comprises selectively adjusting a probe-light focal depth of the probe light.

4 . The method of claim 1 , wherein the step of selectively locating the probe-light focal point of the probe light on the surface comprises selectively adjusting a spatial location of a probe-light optical output of the probe light relative to the surface.

5 . The method of claim 1 , wherein the step of selectively angularly orienting the probe light normal to the surface comprises selectively adjusting a probe-light projection angle of the probe light.

6 . The method of claim 1 , wherein the step of selectively angularly orienting the probe light normal to the surface comprises selectively adjusting a spatial orientation of a probe-light optical output of the probe light relative to the surface.

7 . The method of claim 1 , further comprising a step of defining a pump-light spot on the surface with the pump light that has a pump-light spot size between one millimeter and ten millimeters, based on the spatial location determined for the surface.

8 . The method of claim 7 , wherein the step of defining the pump-light spot on the surface comprises at least one of selectively shaping the pump light, selectively adjusting a pump-light focal depth of the pump light, and selectively adjusting a spatial location of a pump-light optical output of the pump light relative to the surface.

9 . The method of claim 1 , further comprising a step of selectively angularly orienting the pump light at a predetermined angular orientation relative to the surface, based on the spatial orientation determined for the surface.

10 . The method of claim 9 , wherein the step of selectively angularly orienting the pump light at a predetermined angular orientation relative to the surface comprises adjusting a pump-light projection angle of the pump light.

11 . The method of claim 9 , wherein the step of selectively angularly orienting the pump light at a predetermined angular orientation relative to the surface comprises selectively adjusting a spatial orientation of a pump-light optical output of the pump light relative to the surface.

12 . The method of claim 1 , further comprising steps of:
moving the positioning light over the surface along a scan path; moving the pump light and the probe light over the surface along the scan path; determining a change in at least one of the spatial location and the spatial orientation of the surface along the scan path from regular evaluation of the positioning light reflected back from the surface when moving the positioning light over the surface; consistently maintaining the probe-light focal point of the probe light located on the surface, in response to the change in the spatial location determined for the surface, when moving the probe light over the surface; and consistently maintaining the probe light angularly oriented normal to the surface, in response to the change in the spatial orientation determined for the surface, when moving the probe light over the surface.

13 . The method of claim 12 , wherein the step of consistently maintaining the probe-light focal point of the probe light located on the surface comprises selectively adjusting a probe-light focal depth of the probe light when moving the probe light over the surface.

14 . The method of claim 12 , wherein the step of consistently maintaining the probe light angularly oriented normal to the surface comprises selectively adjusting a probe-light projection angle of the probe light when moving the probe light over the surface.

15 . The method of claim 12 , wherein the step of consistently maintaining the probe-light focal point of the probe light located on the surface comprises selectively adjusting a spatial location of a probe-light optical output of the probe light relative to the surface when moving the probe light over the surface.

16 . The method of claim 12 , wherein the step of consistently maintaining the probe light angularly oriented normal to the surface comprises selectively adjusting a spatial orientation of a probe-light optical output of the probe light relative to the surface.

17 . The method of claim 12 , further comprising consistently maintaining a spot, defined by the pump light, on the surface that has a spot-size between one millimeter and ten millimeters, in response to the change in the spatial location determined for the surface, when moving the pump light over the surface.

18 . The method of claim 12 , further comprising consistently maintaining the pump light angularly oriented at a predetermined angular orientation relative to the surface, in response to the change in the spatial orientation determined for the surface, when moving the pump light over the surface.

19 . A method for testing a structure using laser ultrasound, the method comprising steps of:
directing positioning light on a surface of the structure; determining a spatial location and a spatial orientation of the surface from an evaluation of the positioning light reflected back from the surface; selectively angularly orienting pump light at a predetermined angular orientation relative to the surface, based on the spatial orientation determined for the surface; directing the pump light onto the surface to form a pump-light spot having a predetermined pump-light spot size, based on the spatial location determined for the surface; selectively locating a probe-light focal point of probe light on the surface, based on the spatial location determined for the surface; selectively angularly orienting the probe light normal to the surface, based on the spatial orientation determined for the surface; directing the probe light onto the surface; generating ultrasonic waves in the structure with the pump light; and detecting a response to the ultrasonic waves with the probe light.

20 . The method of claim 19 , wherein the pump-light spot size of the pump-light spot is between one millimeter and ten millimeters.

21 . The method of claim 20 , wherein the step of defining the pump-light spot on the surface comprises at least one of selectively shaping the pump light, selectively adjusting a pump-light focal depth of the pump light, and selectively adjusting a spatial location of a pump-light optical output of the pump light relative to the surface.

22 . The method of clai

Assignees

• Boeing Co
• Univ Washington

Inventors

• Bingham Jill P
• Georgeson Gary E
• Motzer William P
• Stewart Alan F
• O'Donnell Matthew
• Pelivanov Ivan

Classifications

• G01N21/1702

  with opto-acoustic detection, e.g. for gases or analysing solids · CPC title

• G01N29/11

  by measuring attenuation of acoustic waves · CPC title

• G01N2291/0231

  Composite or layered materials · CPC title

• G01N2021/1706

  in solids · CPC title

• G01N29/2418 Primary

  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) · CPC title