The need to correct for systematic errors is recognized. Currently, the following technique is used. During the decoding process, the label is scanned for a known character, such as a center character. A systematic error correction value is calculated by comparing the measured width of the center character bars with a reference width for those bars. The error correction value is then applied uniformly across the label.
This technique assumes that the error itself is uniform across the width of the label. That assumption may not always be correct. For example, it is possible for an ink shrink condition at one end of a label to change to an ink spread condition at the opposite end of the label. A correction based on the characteristics of the center character would not be helpful in reading such a label.
USPTO Backgrounds
USPTO Backgrounds