Patent ID: 6330354
Filing Date: 2001-12-11
Classification: G01N,G06T

Abstract:
A method of analyzing visual inspection image data to find defects on a device under test, comprising the steps of:a) providing a plurality of good devices;b) imaging each of said good devices to provide a plurality of images of said good devices, said images of said good devices each comprising pixels;c) comparing value of a first image parameter of each pixel of each good device to a first threshold value and converting said value to black or to white depending on whether said value is above or below said first threshold value;d) deriving a device template image from said plurality of converted images of said good devices, said device template image comprising a device template image pixel corresponding to each good device pixel for said first image parameter;e) providing the device under test;f) imaging the device under test, to provide an image of the device under test comprising pixels corresponding to said pixels of said good devices;g) subtracting said first image parameter of said device under test pixel by pixel from said template image to provide a difference image for said first image parameter;h) comparing the value of each pixel of said difference image to a second threshold value;i) converting the value of each pixel to black or white depending on whether the value of that pixel is above or below the second threshold value to generate a final corrected difference image; andj) identifying a defect on the device under test from said final corrected difference image.