Automated print inspection for cylindrical surfaces

The objective of this research was to determine the criteria for automated inspection of a string of alphanumeric characters printed directly to the surfaces of cylindrical containers. The technical problems encountered, because a curved surface was used instead of a flat surface, were container positioning for locating surface features, character position compensation due to curvature, resolution limits defined for sensor and reflected illumination. Automated print inspection requires the use of machine vision to perform the registration of characters, template comparison for correct text being produced and the interrogation of the individual characters for correctness, position, size and type.