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Method and apparatus for 3-dimensional vision and inspection of ball and like protrusions of electronic components

  • US 8,885,040 B2
  • Filed: 03/30/2007
  • Issued: 11/11/2014
  • Est. Priority Date: 06/21/2006
  • Status: Active Grant
First Claim
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1. A method for 3-dimensional vision inspection of objects, including microelectronic components, having protrusions as features to be inspected, wherein said protrusions having non-planar surfaces and/or surface curvatures, said method comprising the steps of:

  • (a) providing a stereo camera system comprising at least a pair of cameras arranged in a stereovision configuration, wherein the first camera captures a side view of said object, and the second camera captures an opposite side view of said object;

    (b) calibrating said stereo camera system to determine the interior parameters of said respective cameras and exterior parameters, or relative pose including position and orientation, of the second camera with respect to the first camera, wherein the interior parameters include focal length, optics center, distortion coefficients, and sensor cell size and the exterior parameters or the relative pose includes roll angle, tilt angle, pan angle, and translation along X axis, Y axis, and Z axis respectively of one camera with respect to the other camera;

    (c) forming a rectified stereo camera system with a rectified camera coordinate system from the parameters of said real stereo camera system determined above, and determining the interior parameters of said respective rectified cameras and exterior parameters, or relative pose including position and orientation, of the second rectified camera with respect to the first rectified camera, wherein, the optical centers of the rectified cameras are the same as those of said stereo cameras, but the rectified cameras are rotated such that both rectified cameras are in parallel and their X axes are collinear, and the orientation of the rectified cameras is defined by the cross product of line connecting the optical centers of said stereo cameras, and line of intersection of the image planes of said stereo cameras, and both rectified cameras have the same focal length;

    (d) using said stereo camera system to capture a pair of images of said object comprising two side views of surface curvatures of each of the protrusions of said object;

    (e) rectifying said pair of images to produce a pair of rectified images as captured by said rectified stereo camera system, wherein, the rectified images are on the image planes of the rectified cameras;

    (f) determining a pair of conjugate points for the tip of each protrusion in the rectified images; and

    (g) determining the location of each protrusion, which include x, y, and z coordinates, in the rectified camera coordinate system based on said pair of conjugate points and said interior and exterior parameters of said rectified stereo camera system for 3-dimensional vision inspection of said objects.

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