1. An image processing unit for performing an arithmetic operation between a reference image and a search image, upon receipt of the reference image and the search image, said image processing unit having an image processing section comprising: a first multiplication section for computing a square of a pixel value of the reference image; an addition section for adding square value of the pixel values of the reference image obtained by said first multiplication section over a plurality of pixels; a first square root computing section for computing a square root of an additional value over a plurality of pixels of the square value of the pixel values of the reference image obtained by said addition section to determine a norm of the reference image; a product-sum operation section used on a common basis for both an addition of square values of pixel values of the search image over a plurality of pixels and an addition of multiplication values of pixel values of pixels associated with the search image and the reference image over a plurality of pixels; a second square root computing section for computing a square root of an additional value over a plurality of pixels of the square value of the pixel values of the search image obtained by said product-sum operation section to determine a norm of the search image; a second multiplication section for multiplying the norm of the reference image obtained by said first square root computing section and the norm of the search image obtained by said second square root computing section together; and a division section for dividing an additional value of multiplication values of pixel values of pixels associated with the search image and the reference image over a plurality of pixels obtained by said product-sum operation section by a multiplication value between the norm of the reference image and the norm of the search image obtained by said second multiplication section to obtain a normalization correlation value.