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Method for measuring the contour of a surface

  • US 5,500,737 A
  • Filed: 07/21/1993
  • Issued: 03/19/1996
  • Est. Priority Date: 07/21/1993
  • Status: Expired due to Fees
First Claim
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1. A method for measuring the contour of a surface, comprising the steps of:

  • (a) projecting a line of light on the surface to illuminate a selected contour feature of the surface;

    (b) generating an image of the selected contour feature illuminated by the line of light by imaging an off-axis projection of light reflected from the illuminated contour feature; and

    (c) evaluating the selected contour feature by comparing the image against a predetermined specification;

    wherein any distortion and keystone effect in the image caused by off-axis imaging of the illuminated contour feature is corrected by the steps of;

    positioning a square grid within the field of view of an image generating means to provide an off-axis image of the square grid;

    superimposing an electronically produced grid corresponding to the square grid over the off-axis image of the square grid;

    adjusting the vertical and horizontal grid lines of the electronically produced grid to match the convergence of the vertical and horizontal grid lines of the off-axis square grid image;

    storing a vertical and a horizontal convergence adjustment parameter corresponding to a displacement of the electronically produced grid lines to match the grid lines of the off-axis image;

    adjusting the vertical and horizontal grid lines of the electronically produced grid to match the spacing between the vertical and horizontal grid lines of the off-axis square grid image; and

    storing a vertical and horizontal spacing adjustment parameter corresponding to a displacement of the electronically produced grid lines to match the grid lines of the off-axis image, the convergence adjustment parameters and the spacing adjustment parameters being used to correct the off-axis image of the illuminated contour feature.

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