CUTOFF CONTROL SYSTEM

The invention provides a cutoff control system having a capture range equal to the length of the image (signature) which is highly tolerant of spurious transitions, such as lateral shifting and instantaneous interruptions of the web. A highly pipelined hardware correlation unit, cooperating with several high speed RAM devices having independent address generators, is used to cross-correlate new patterns with a reference pattern. An illustrated system for relating a cyclical machine operation to the position of images on a web includes position adjustment means (24,30,84) responsive to control signals for varying the effective position of the machine operation along the moving web, means (34,40,50) for generating image signatures indicative of the image at respective sampling intervals during the matching operation cycle for respective machine cycles, means (56,58,68,72) for selectively generating reference pattern indicia from a first image signature and for selectively generating comparative indicia from a successive image signature, means (71) for generating correlation cooeficients in accordance with the differences between the reference pattern and shifted versions of the comparative indicia, means (68,69,70) for processing the correlation coefficients to determine which of the comparative indicia produced the largest correlation coeficient and generating an indicating signal in response thereto, and means (80) for generating the control signals to the position adjustment means in accordance with the indicating signal.