1. A method for determining a location of a peak of a correlation function generated by comparing a first high-spatial-frequency image to a second high-spatial-frequency image, the correlation function having a regular background portion and a peak portion, the method comprising: comparing a first high-spatial-frequency image to a second high-spatial-frequency image to determine at least one correlation function value for a set of at least one sparsely distributed correlation function value point of the correlation function; and analyzing at least one of the at least one correlation function value to identify at least one correlation function value point that lies within the peak portion.