Automated visual inspection of electronic component leads prior to placement

• US 5,185,811 A
• Filed: 01/21/1992
• Issued: 02/09/1993
• Est. Priority Date: 12/27/1990
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Flickner, Myron D., Kelly-Mahaffey, William L., Wattenbarger, Henry E., Stafford, James M., Beers, Gregory E., Polk, Darryl R.
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): KELLEY, CHRISTOPHER S
• Application Number:
  US07/825,434
• Time in Patent Office: 385 Days
• Field of Search: 382/8, 382/18, 382/22, 382/45, 382/48
• US Class Current: 382/151
• CPC Class Codes: G06T 2207/30141 Printed circuit board [PCB]
• CPC Class Codes: G06T 7/0008 checking presence/absence
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80

Abstract

A method and apparatus utilizing one or two cameras are described for visually inspecting a polygonal component located at the end of the robotic end effector for determining presence, position and orientation of component leads prior to placement. Image processing improvements are provided for decreasing computational complexity by representing two dimensional image areas of interest, and each containing leads along one side of a component, by one dimensional summation profiles.

Claims

1. Apparatus for inspecting leaded electronic components comprising:

means for acquiring a two dimensional array of grey level image data including two cameras and means for combining images therefrom, said means for combining including;

means for mapping images from said two cameras to a common coordinate system;

means for determining overlap between said images;

means for computing to sub-pixel accuracy a centroid of a component,

means for operating on preselected subarrays of said array of image data for forming a plurality of one dimensional summation profiles; and

vision logic means for operating on said summation profiles.

2. A method for visually inspecting a leaded component comprising the steps of:

capturing images of the component with a plurality of cameras;

digitizing images so captured;

mapping portions of said digitized images corresponding to locations where leads are expected to a single coordinate system;

determining overlap between mapped image portions;

finding lead centroid position to sub-pixel accuracy in each mapped image portion;

mapping lead positions from each image to a common coordinate system;

identifying overlapping leads; and

calculating component position and orientation as a function of lead centroids found.

3. The method of claim 2 wherein the finding step comprises:

developing one dimensional summation profiles corresponding to each mapped image portion;

correlating profile peaks to individual lead centers;

correcting profile peaks for light gradients; and

excluding false peaks.

4. The method of claim 3 wherein said developing step comprises:

summing gray level pixel values in rows or columns as a function of which is substantially parallel to expected lead axis.