Abstract: Machine vision methods for inspection of semiconductor die lead frames include the steps of generating a first image of the lead frame, generating a second image of the lead frame and any defect thereon, and subtracting the second image from the first image. The methods are characterized in that the second image is generated such that subtraction of it from the first image emphasizes the defect with respect to the lead frame.

Abstract: An improved machine vision apparatus, of the type having a search element capable of estimating the location of a template image in a candidate image, includes an element that accepts signals representative of the template and of a candidate image. Those signals are applied to the search element to obtain its estimate of location. A correction element responds to the resulting approximation by the location-finder for generating a signal representative of more exacting location based on a known relationship between the location-finder output and more exacting locations of the template in a model of the candidate image.