Patent ID: 6289117
Filing Date: 2001-09-11
Classification: G06T

Abstract:
A computer-based method of analyzing an image of actual pattern of discrete balls of a ball grid array with respect to a model representing a predefined ideal pattern of the balls arranged on a regular grid, the image comprising a set of digital data representing an array of pixels of the image, the method comprisingarranging the model to express locations of the balls in terms of vectors which represent standard spacings of the balls along two dimensions and fill information indicating the existence or nonexistence of a ball at each location of an array defined by the vectors,performing initial processing of only a portion of the image associated with ones of the balls located in an original neighborhood within the image to determine information about an affine transformation of the actual pattern of the balls relative to the predefine ideal pattern, the initial processing comprisingidentifying a first one of the balls in the image,identifying locations of adjacent other balls in the original neighborhood relative to the first ball,expressing locations of the adjacent other balls relative to the first ball in angular coordinates, andmatching the angular coordinate information against the model to determine a rotational element of the affine transformation, andperforming additional processing of other portions of the image based on the results of the initial processing, including deriving information about additional ones of the balls located in other portions of the image that are farther away from the first ball than are the balls in the original neighborhood, and wherein less processing is required for balls that are more distant from the first ball, andperforming ball inspection using the image, to compare the balls in the image against a predefined standard.