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Method for inspecting components having complex geometric shapes

  • US 5,345,514 A
  • Filed: 09/16/1991
  • Issued: 09/06/1994
  • Est. Priority Date: 09/16/1991
  • Status: Expired due to Term
First Claim
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1. A method for inspecting a component having a plurality of similarly shaped structural portions, comprising the steps of:

  • (a) scanning a surface of at least one of the similarly shaped structural portions with an eddy current probe means to induce eddy currents in the component;

    (b) generating a two-dimensional image of the at least one portion from eddy current signals received during scanning, the image including a multiplicity of pixels arranged in a two-dimensional matrix array and each pixel having a gray scale intensity responsive to the eddy current induced in the component at a component location corresponding to a position of the pixel in the two-dimensional matrix array;

    (c) preprocessing the image to substantially reduce any signals caused by geometrical characteristics and background noise common to all of the similarly shaped structural portions;

    (d) identifying any suspected defect regions in the two-dimensional image from corresponding regions in the preprocessed image of step (c);

    (e) determining a defect signal from the gray scale intensities for each suspected defect regions in the two-dimensional image; and

    (f) rejecting the component if any defect signal exceeds a predetermined reference value, wherein step (c) comprises the steps of;

    (c1) repeating steps (a) and (b) to generate a two-dimensional image for a second and third similarly shaped structural portion;

    (c2) selecting a test portion and an associated test image, a first reference portion and an associated first reference image, and a second reference portion and an associated second reference image from the three similarly shaped portions;

    (c3) taking a difference between the first reference image and the test image to provide a first resulting image by taking a difference between the gray scale intensity of each pixel of the first reference image and the gray scale intensity of a corresponding pixel of the test image;

    (c4) taking a difference between the second reference image and the test image to provide a second resulting image by taking a difference between gray scale intensities of corresponding pixels of each image;

    (c5) converting each of the first and second reference images from a gray scale image to respective first and second binary images; and

    (c6) combining the first and second binary images by a logic AND operation to provide a preprocessed composite binary image.

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