Patent ID: 6330353
Filing Date: 2001-12-11
Classification: G06K,G06T

Abstract:
A method for localization refinement of inspection patterns comprising the steps of:providing a template image comprising pixels in a pattern, each pixel having an intensity; partitioning the template image into blocks of pixels;determining a reliability measure for each pixel in each block, the reliability measure being based upon a sum of the squares error and a polynomial fitting function for the pixels in the block;identifying a pixel location for each block having a largest reliability measure as a feature point for each block;providing an input image having a same pattern of pixels as the template image, the input image having an initial shift and rotation relative to the template image;modifying optical flow constraint equations to account for illumination changes in the input image; andminimizing an energy function formed by weighting a sum of the modified optical flow constraints at locations of the pixels of both the template image and the input image to determine a shift and rotation between the pattern of the template image and the input image for determining misalignments between the template image and the input image for an inspection process the minimizing step being performed at locations of the feature points of the template image to determine the shift and rotation between the template image and the input image.