TWO-DIMENSIONAL BAR CODE SCANNING METHOD AND ITS SCANNING DEVICE

摘要

PURPOSE: To automatically line up the visual field of a two-diensional bar code reader to a two-dimensional bar code symbol arranged in an optional direction by providing a unique and searchable pattern arranged along at least one side. CONSTITUTION: This laser scanner scans a symbol by means of a laser scanning line extended through a boundary pattern (PDF 417 start code word), measures the length of a start code word detected by means of the scanning line and rotates the scanning line by a prescribed quantity. This is repeated by prescribed number of times to determine a rotation angle minimizing the length of the code word by applying the method of least squares of the measured code word length and the rotation angle. Next, the raster pattern is rotated to a determined rotation angle and lined up with the symbol for following scanning and decoding.