Abstract: An apparatus for scanning colored registration marks printed on a moving web by a plurality of printing cylinders of a printing press is provided with a photoemitter for generating a beam of light directed at the moving web, a detector for detecting the amount of light reflected from the moving web and generating a reflectance signal having a magnitude relating to the amount of light, an A/D converter for periodically sampling the reflectance signal to generate a number of scan values, a memory for storing the scan values, and a baseline generator for determining a baseline level of the reflectance signal. The baseline generator may include means for assigning each of the scan values to one of a plurality of predetermined ranges of values based on the magnitudes of the scan values, means for determining a baseline range from the plurality of the predetermined ranges based on the range having the largest number of the scan values, and means for determining the baseline level based upon the baseline range.

Abstract: An apparatus for scanning colored registration marks printed on a moving web by a plurality of printing cylinders of a printing press is provided with a photoemitter for generating a beam of light directed at the moving web, a detector for detecting the amount of light reflected from the moving web and generating a reflectance signal having a magnitude relating to the amount of light, an A/D converter for periodically sampling the reflectance signal to generate a number of scan values, a memory for storing the scan values, and a baseline generator for determining a baseline level of the reflectance signal. The baseline generator may include means for assigning each of the scan values to one of a plurality of predetermined ranges of values based on the magnitudes of the scan values, means for determining a baseline range from the plurality of the predetermined ranges based on the range having the largest number of the scan values, and means for determining the baseline level based upon the baseline range.

Abstract: A pre-registration system for a printing press may be provided with a first detector for detecting an angular position of a first rotatable printing cylinder by sensing when a reference mark disposed on the first printing cylinder is in a predetermined angular position, a second detector for detecting an angular position of a second printing cylinder by sensing when a reference mark of the second printing cylinder is in a predetermined angular position, and an adjustment mechanism for automatically adjusting the angular position of one of the printing cylinders based on the circumference, a web distance, and the angular position of one of the printing cylinders. The adjustment mechanism may adjust the angular position based upon a stored phase data relating to the web distance and the circumference.