External lead shape measurement apparatus for measuring lead shape of semiconductor package by using stereoscopic vision

A lead shape measurement apparatus having a plurality of imaging devices in which at least two imaging devices image a lead shape from different directions, and forming an image of said lead shape in a stereoscopic vision, comprising:

• a first perspective imaging device for photographing external leads to be measured, from an oblique direction;
• a second perspective imaging device for photographing external leads to be measured, from an oblique direction different from that of said first perspective imaging device so as to include a same photographic field of vision as said first perspective imaging device;
• first measurement point determination means for determining as a measurement sampling point a center point of two intersecting virtual straight lines which intersect two ridges of said external leads to be measured in a first image plane by photography of said first perspective imaging device;
• a second measurement point determination means, in a second image plane by said second perspective imaging device, for setting an epipolar line on the basis of sight lines when said measurement sampling point of said first imaging device is photographed, and for determining a center point of two intersecting virtual straight lines which intersect two ridges of said external leads to be measured in said second image plane and which exists upon said epipolar line and for further determining said center point in said second image plane to be specified as a same point as said measurement sampling point;
• and wherein:
• a plurality of measurement sampling points are determined to calculate three-dimensional coordinates determined, with said three-dimensional coordinates being used as the basis for measurement of a three-dimensional shape of said external leads to be measured.