Cross correlation between a reference image frame and a comparison image frame determine the direction of motion relative to x and y orthogonal axes for a pointing device that uses optical imaging to monitor movement relative to a surface. Pixel data for a portion of the surface are loaded into a buffer...http://www.google.com.tw/patents/US20030058218?utm_source=gb-gplus-share專利 US20030058218 - Tracking pointing device motion using a single buffer for cross and auto correlation determination
