Image-Based Bar Code Reading

For letter mail, SRI developed a Wide-Area Bar-Code Reader (WABCR) system that reads the POSTNET bar code (which contains ZIP Code information). Using a CCD linear-array scanner to capture mail-piece images, the WABCR finds the bar code wherever it is located on the mail piece. Bulk mailers can therefore print the bar code as part of the address block, which can be positioned anywhere on the envelope. Because SRI's algorithm finds bar codes printed over advertising and patterned backgrounds, it is more reliable than traditional processing methods such as those based on fixed thresholds. SRI has also developed gray-level image processing techniques to locate and interpret bar codes. These techniques have an improved immunity to the presence of text and background interference, and tolerate poorly printed and skewed bar-code patterns (Figure 1).