METHOD FOR QUALITATIVELY EVALUATING MATERIAL

A method for qualitatively evaluating material with at least one identification characteristic, whose position can vary within an expectation range designated by tolerance limits, involves the use of at least one illuminating device, at least one photoelectric sensor and an evaluating device. At least one background reference value and at least one mask reference are stored in the evaluating device. The background reference represents the characteristics of a printed image, particularly the gray scale value, in at least one portion which surrounds the identification characteristic. The mask reference represents the geometrical contour of the identification characteristic. During inspection of the printed material, differential image data is found, at least from the expectation range, from the actual image data, and from the background reference value in the evaluating device. The actual position of the identification characteristic is subsequently derived in the evaluating device.