Importance

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Abstract

Method and apparatus for selecting a threshold for use by a boundary tracker to locate a crescent on a bonded lead involves creating a two-dimensional inspection window along the angle of the wire in a post-bond image of a bonded wire in order to generate a one-dimensional projection; generating a one-dimensional projection by summing each column of pixels in the inspection window in the direction of the wire angle and computing an average grey value for each column; and applying an edge-detection to the one-dimensional projection to locate the edges of the wire. If an edge point falls directly in the center of a pixel of the one-dimensional projection, the grey value for that edge point is considered to be the grey value of that pixel. If the edge falls between pixels, the edge's grey value is determined by the fractional pixel position of the edge point in the projection. The grey values of the left and right edge points are averaged and used as the threshold value. For more accurate threshold selection or if reflective stripes or confusing edges are likely to occur in the parts being inspected, the same steps are performed using a clipped difference image of the bonded wire instead of a post-bond image.

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First Claim