1. An image processing system responsive to a model signal comprising model pixel values and an image signal comprising image pixel values for generating a score signal representative of a degree of correlation between said model signal and said image signal, said system including: A. cache memory means for storing for addressable access algebraic squares corresponding to any of model pixel values, image pixel values and sums of image and model pixel values, said cache memory means being responsive to an address signal based on any such value for accessing and generating a signal representative of a corresponding algebraic square, B. central processing unit (CPU) means, coupled to said cache memory means, for processing said model signal and said image signal to generate said score signal, said CPU means including (i) model square means responsive to said model signal for applying to said cache memory means address signals based on at least selected ones of said model pixel values to generate a .SIGMA..SIGMA.m.sup.2 signal comprising sums of the squares of those values, (ii) image square means responsive to said image signal for applying to said cache memory means address signals based on at least selected ones of said image pixel values to generate a .SIGMA..SIGMA.i.sup.2 signal comprising sums of the squares of those values, and (iii) sum square means responsive to said model and image signals for applying to said cache memory means address signals based on sums of at least selected corresponding ones of said image pixel values and model pixel values to generate a .SIGMA..SIGMA.(i+m).sup.2 signal comprising sums of the squares of those sums, (iv) correlation means, coupled to said model square means, said image square means and said sum square means, for generating said score signal as a function of values in said .SIGMA..SIGMA.m.sup.2 signal, said .SIGMA..SIGMA.i.sup.2 signal, and said .SIGMA..SIGMA.(i+m).sup.2 signal.