1. A computer-implemented method for optimally registering a current image and a reference image to provide for detection of differences therebetween, said method comprising the steps of: retrieving a reference image from a storage device; processing the reference image to calculate an inverse covariance matrix for each of a plurality of image subareas of the reference image; selecting a plurality of candidate image subareas from the plurality of image subareas based upon the relative values of the inverse covariance matrices for use in registering the current image to the reference image; processing the plurality of candidate image subareas to generate a list of subareas that optimally register the current image; processing the reference image to calculate covariance propagation weights for the reference image that are indicative of the error covariance between the reference image and the current image; processing the reference image to calculate the covariance of polynomial error coefficients of each of the candidate subareas using a priori covariance of polynomial error coefficients and the calculated covariance propagation weights; processing the list of subareas, the inverse covariance matrices, the covariance propagation weights, and the covariance of polynomial error coefficients to produce signals indicative of a set of reference subareas that are used to optimally register the current image; selecting a set of subareas from the current image that correspond to the set of reference subareas; correlating the selected set of subareas from the current image to the set of reference subareas to produce difference signals indicative of the difference in registration between the reference image and the current image; and outputting the difference signals to provide data indicative of the differences in registration between the reference image and the current image.