A pre processor stores digital voltage values of respective pixels of {HEAD ~ an image} received from {TAIL ~ a pre processor} in a memory, performs a pre process for the digital voltage values of respective pixels sequentially received from the memory, thereby producing a pre processed current image, and extracts a pre processed current central image from the pre processed current image 
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A pre processor stores digital voltage values of respective pixels of { HEAD ~ an image } received from { TAIL ~ a pre processor } in a memory , performs a pre process for the digital voltage values of respective pixels sequentially received from the memory , thereby producing a pre processed current image , and extracts a pre processed current central image from the pre processed current image
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH