Method and apparatus for use in inspection of objects

• US 6,229,872 B1
• Filed: 12/22/1998
• Issued: 05/08/2001
• Est. Priority Date: 12/22/1998
• Status: Expired due to Term

• Current Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Amos, Jay M.
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): Dunn, Drew A.
• Application Number:
  US09/218,577
• Time in Patent Office: 868 Days
• Field of Search: 378/57, 378/59, 378/58, 378/197, 73/618, 73/622, 73/633, 356/237.1
• US Class Current: 378/58
• CPC Class Codes: G01N 23/00 Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00

Abstract

A method and an apparatus generate a plurality of inspection signals each indicative of an internal physical characteristic of a portion of an object. Each of the inspection signals is generated with a different orientation relative to the portion of the object. A signal is generated indicative of a measure of correlation between the inspection signals. The method and the apparatus can be used to reduce the effect of noise and/or distortion in regard to inspection of objects. In one detailed embodiment, the inspection signals are x-ray images indicative of a density of an object. The x-ray images are processed to identify indications in the x-ray images that indicate a density associated with a defect. The indications in the images are then compared to each other to determine whether there is a correlation between the indications. Low correlation between the indications tends to indicate the presence of distortion in the inspection signals. High correlation between the indications indicates lack of distortion in the x-ray images. Such method and the apparatus are used to better distinguish between a portion of an x-ray indicative of distortion and a portion of an x-ray image indicative of defects, in reasonably rapid fashion, thereby making inspection of objects having relatively large, randomly oriented grains economical and practical.

Claims

1. A method for use in inspecting an object, the method comprising the steps of:

generating a plurality of inspection signals each indicative of at least one internal physical characteristic of a portion of the object;

changing orientation for generating each of the plurality of inspection signals, wherein for each of the plurality of inspection signals the step of generating includes the steps of;

directing a source signal at the portion of the object;

detecting an output signal from the portion of the object, the output signal being indicative of the at least one internal physical characteristic of the portion of the object, the step of directing and the step of detecting being performed using an orientation relative to the portion of the object; and

generating the inspection signal in response to the output signal; and

generating, in response to the plurality of inspection signals, a signal indicative of at least one measure of correlation between the plurality of inspection signals to reduce effects of distortion on the results of the inspection for better distinguishing between distortion and defects in inspected objects.

2. The method of claim 1 wherein the object is at least three square inches in area.

3. The method of claim 1 wherein the output signals from the portion of the object are transmitted through the portion of the object.

4. The method of claim 1 wherein the step of detecting comprises detecting with a detector having a plurality of detector elements disposed generally within a plane, and the different orientations used in generating the plurality of inspection signals are provided by translating at least one of the detector and the object in a direction parallel to the plane.

5. The method of claim 1 wherein the plurality of inspection signals comprises at least three inspection signals.

6. A method for use in inspecting an object, the method comprising the steps of:

generating a plurality of inspection signals each indicative of at least one internal physical characteristic of a portion of the object;

changing orientation for generating each of the plurality of inspection signals, wherein for each of the plurality of inspection signals the step of generating includes the steps of;

directing a source signal at the portion of the object;

detecting an output signal from the portion of the object, the output signal being indicative of the at least one internal physical characteristic of the portion of the object, the step of directing and the step of detecting being performed using an orientation relative to the portion of the object; and

generating the inspection signal in response to the output signal; and

generating, in response to the plurality of inspection signals, a signal indicative of at least one measure of correlation between the plurality of inspection signals;

wherein the step of generating the signal indicative of the at least one measure of correlation between the plurality of inspection signals comprises the steps of;

providing at least one reference indicative of at least one measure of the at least one internal physical characteristic;

determining for each of the plurality of inspection signals, and in response to the at least one reference, no less than zero indications of the inspection signal indicating at least one physical characteristic associated with the at least one measure of the at least one internal physical characteristic; and

generating, in response thereto, the signal indicative of the at least one measure of correlation between the plurality of inspection signals.

7. The method of claim 6 wherein the step of generating the signal indicative of the at least one measure of correlation between the plurality of inspection signals further comprises the steps of:

determining for each of the plurality of inspection signals, a position and a size of at least one of the no less than zero indications;

comparing the position and the size of the at least one of the no less than zero indications of at least one of the plurality of inspection signals with the position and the size of the at least one of the no less than zero indications of at least one other of the plurality of inspection signals; and

generating, in response thereto, the signal indicative of the at least one measure of correlation between the plurality of inspection signals.

8. The method of claim 7 wherein the object is at least three square inches in area, the output signals from the portion of the object are transmitted through the portion of the object, the step of detecting comprises detecting with a detector having a plurality of detector elements disposed generally within a plane, and the different orientations used in generating the plurality of inspection signals are provided by translating at least one of the detector and the object in a direction parallel to the plane.

9. A method for use in inspecting an object, the method comprising the steps of:

generating a plurality of inspection signals each indicative of at least one internal physical characteristic of a portion of the object;

changing orientation for generating each of the plurality of inspection signals, wherein for each of the plurality of inspection signals the step of generating includes the steps of;

directing a source signal at the portion of the object;

detecting an output signal from the portion of the object, the output signal being indicative of the at least one internal physical characteristic of the portion of the object, the step of directing and the step of detecting being performed using an orientation relative to the portion of the object; and

generating the inspection signal in response to the output signal; and

generating, in response to the plurality of inspection signals, a signal indicative of at least one measure of correlation between the plurality of inspection signals;

wherein the step of generating the signal indicative of the at least one measure of correlation between the plurality of inspection signals comprises the steps of;

providing at least one reference indicative of at least one density associated with at least one defect;

determining for each of the plurality of inspection signals, and in response to the at least one reference, no less than zero indications of the inspection signal indicating at least one density associated with the at least one defect; and

generating, in response thereto, the signal indicative of the at least one measure of correlation between the plurality of inspection signals.

10. The method of claim 9 wherein the step of generating the signal indicative of the at least one measure of correlation between the plurality of inspection signals further comprises the steps of

determining for each of the plurality of inspection signals, a position and a size of at least one of the no less than zero indications;

comparing the position and the size of the at least one of the no less than zero indications of at least one of the plurality of inspection signals with the position and the size of the at least one of the no less than zero indications of at least one other of the plurality of inspection signals; and

generating, in response thereto, the signal indicative of the at least one measure of correlation between the plurality of inspection signals.

11. The method of claim 10 wherein the object is at least three square inches in area, the output signals from the portion of the object are transmitted through the portion of the object, the step of detecting comprises detecting with a detector having a plurality of detector elements disposed generally within a plane, and the different orientations used in generating the plurality of inspection signals are provided by translating at least one of the detector and the object in a direction parallel to the plane, and further comprising the step of using the method to inspect.

12. An apparatus for use in an inspection system to inspect an object, the inspection system having a source and a detector, the apparatus comprising:

means for providing a plurality of orientations of the source and the detector relative to a portion of the object, each of the plurality of orientations being different than the others of the plurality of orientations,

wherein at each of the plurality of orientations the source provides a source signal directed at the portion of the object and the detector detects an output signal from the portion of the object, the output signal being indicative of at least one internal physical characteristic of the portion of the object, and the detector generates, in response to the output signal, one of a plurality of inspection signal indicative of the at least one internal physical characteristic of the portion of the object; and

means for generating, in response to the plurality of inspection signals, a signal indicative of at least one measure of correlation between the plurality of inspection signals to reduce effects of distortion on the results of the inspection for better distinguishing between distortion and defects in inspected objects.

13. The apparatus of claim 12 wherein the means for providing a plurality of orientations includes means for positioning the object between the source and the detector.

14. The apparatus of claim 12 wherein the plurality of inspection signals comprises at least three inspection signals.

15. An apparatus for use in an inspection system to inspect an object, the inspection system having a source and a detector, the apparatus comprising:

means for providing a plurality of orientations of the source and the detector relative to a portion of the object, each of the plurality of orientations being different than the others of the plurality of orientations,

wherein at each of the plurality of orientations the source provides a source signal directed at the portion of the object and the detector detects an output signal from the portion of the object, the output signal being indicative of at least one internal physical characteristic of the portion of the object, and the detector generates, in response to the output signal, one of a plurality of inspection signal indicative of the at least one internal physical characteristic of the portion of the object; and

means for generating, in response to the plurality of inspection signals, a signal indicative of at least one measure of correlation between the plurality of inspection signals;

wherein the means for generating the signal indicative of the at least one measure of correlation between the plurality of inspection signals comprises;

means for providing at least one reference indicative of at least one measure of the at least one internal physical characteristic; and

means for determining for each of the plurality of inspection signals, and in response to the at least one reference, no less than zero indications of the inspection signal indicating at least one physical characteristic associated with the at least one measure of the at least one internal physical characteristic; and

means for generating, in response thereto, the signal indicative of the at least one measure of correlation between the plurality of inspection signals.

16. The apparatus of claim 15 wherein the means for generating the signal indicative of the at least one measure of correlation between the plurality of inspection signals further comprises:

means for determining for each of the plurality of inspection signals, a position and a size of at least one of the no less than zero indications;

means for comparing the position and the size of the at least one of the no less than zero indications of at least one of the plurality of inspection signals with the position and the size of the at least one of the no less than zero indications of at least one other of the plurality of inspection signals; and

means for generating, in response thereto, the signal indicative of the at least one measure of correlation between plurality of inspection signals.

17. The apparatus of claim 16 wherein the means for providing a plurality of orientations includes means for positioning the object between the source and the detector, the detector has a plurality of detector elements disposed generally within a plane, and the means for providing a plurality of different orientations includes means for translating at least one of the detector and the object in a direction parallel to the plane.

18. An apparatus for use in an inspection system to inspect an object, the inspection system having a source and a detector, the apparatus comprising:

means for providing a plurality of orientations of the source and the detector relative to a portion of the object, each of the plurality of orientations being different than the others of the plurality of orientations,

wherein at each of the plurality of orientations the source provides a source signal directed at the portion of the object and the detector detects an output signal from the portion of the object, the output signal being indicative of at least one internal physical characteristic of the portion of the object, and the detector generates, in response to the output signal, one of a plurality of inspection signal indicative of the at least one internal physical characteristic of the portion of the object; and

means for generating, in response to the plurality of inspection signals, a signal indicative of at least one measure of correlation between the plurality of inspection signals;

wherein the means for generating the signal indicative of the at least one measure of correlation between the plurality of inspection signals comprises;

means for providing at least one reference indicative of at least one density associated with at least one defect;

means for determining for each of the plurality of inspection signals, and in response to the at least one reference, no less than zero indications of the inspection signal indicating at least one density associated with the at least one defect; and

means for generating, in response thereto, the signal indicative of the at least one measure of correlation between the plurality of inspection signals.

19. The apparatus of claim 18 wherein the means for generating the signal indicative of the at least one measure of correlation between the plurality of inspection signals further comprises:

means for determining for each of the plurality of inspection signals, a position and a size of at least one of the no less than zero indications;

means for comparing the position and the size of the at least one of the no less than zero indications of at least one of the plurality of inspection signals with the position and the size of the at least one of the no less than zero indications of at least one other of the plurality of inspection signals; and

means for generating, in response thereto, the signal indicative of the at least one measure of correlation between the indications provided by the plurality of inspection signals.

20. The apparatus of claim 19 wherein the means for providing a plurality of orientations includes means for positioning the object between the source and the detector, the detector has a plurality of detector elements disposed generally within a plane, and the means for providing a plurality of different orientations includes means for translating at least one of the detector and the object in a direction parallel to the plane.